Bottom-up synthetic biology thrives in reverse-engineering a particular biological function using a minimal set of molecular components, like purified proteins.<\/p>\n
Recently, precision technologies, like microfluidics, have been used to recombine functional modules towards multifunctional synthetic cells. Synthetic biology can capitalize on a variety of pre-existing on-chip functions, which greatly increases the scope for complexity in the field.<\/p>\n
Advances in DNA nanotechnology gave rise to a diverse range of fully synthetic functional modules, like DNA-based ion channels or motors, which can replace some protein-based parts.<\/p>\n
Noteworthy progress has been made in achieving large and stable compartments, organelle-like multicompartment systems, and sophisticated cytoskeletal structures.
\nWith the ultimate aim to construct a living cell, bottom-up synthetic biology strives to reconstitute cellular phenomena in vitro \u2013 disentangled from the complex environment of a cell. Recent work towards this ambitious goal has provided new insights into the mechanisms governing life. With the fast-growing library of functional modules for synthetic cells, their classification and integration become increasingly important. We discuss strategies to reverse-engineer and recombine functional parts for synthetic eukaryotes, mimicking the characteristics of nature\u2019s own prototype. Particularly, we focus on large outer compartments, complex endomembrane systems with organelles, and versatile cytoskeletons as hallmarks of eukaryotic life. Moreover, we identify microfluidics and DNA nanotechnology as two technologies that can integrate these functional modules into sophisticated multifunctional synthetic cells.
\nEngineering Eukaryotic Cells from the Bottom up
\nEvery cell found on Earth today originates from a pre-existing cell. In principle, however, the emergence of life on Earth shows that it is possible to engineer life from its molecular constituents. This, in turn, leads to a philosophical question: Can the transition between nonliving and living matter be achieved in a laboratory? The audacious vision of building an entire cell from scratch has recently been transferred into the realm of the possible \u2013 well aware that, if successful, a synthetic cell (see Glossary) would revolutionize our understanding of the origin and the future of life. The quest for a synthetic eukaryote is in the first instance a merely curiosity-driven scientific endeavor with the overarching aim to understand life in greater detail. It may offer means to probe theories on the evolutionary origin of the eukaryotic cell, which remains one of the greatest mysteries in evolutionary biology [1]. Moreover, synthetic eukaryotic cells will also be indispensable for visionary applications, especially when it comes to synthetic phagocytotic systems, programmable drug carriers, or replacements for deficient cells. Towards this end, the young and dynamic field of bottom-up synthetic biology has been successful at dissecting cellular phenomena to study them in isolation. It has produced cellular functional modules, such as energy modules or gene expression modules, with reduced complexity. Several recent reviews portray these developments [2, 3, 4, 5]. A comparison of top-down and bottom-up approaches to synthetic biology is presented in Box 1.<\/p>\n
Box 1<\/p>\n
+
\nBox 1
\nBottom-up versus Top-down Synthetic Biology
\nRealizing the vision of a fully functional synthetic cell, however, will require strategies to recombine the mosaic of functional modules inside cell-like compartments. In this review, we explicitly highlight approaches that, in principle, allow for the stepwise integration of functional modules towards a multifunctional system (Figure 1, Key Figure). Distinguishing such efforts from the certainly not less exciting work towards minimalistic protocells becomes important as the library of functional modules is growing. We propose the integrability as the key criterion according to which synthetic cellular modules should be rated, which will help to compare and contrast achievements in the field. We further propose a classification of synthetic cells according to the pre-existing divide between prokaryotic and eukaryotic cells. The characteristics of a synthetic eukaryote are prescribed by the distinguishing features of nature\u2019s own archetype: (i) large cell size compared to prokaryotes; (ii) complex endomembrane system with multiple organelles; and (iii) distinctive multifunctional cytoskeleton. These three features define the sections of this review as illustrated in Figure 1.
\nLarge Compartment Size
\nTypically tens of microns in size, eukaryotes are on average larger and enclose 100\u201310\u2005000 times greater volumes compared to prokaryotic cells [6]. The physical dimensions have a profound impact on cellular processes affecting, among other things, the surface-to-volume ratio and the diffusion time of reagents. A cell-sized compartment as a physical container of cellular function is thus the most basic unit of a synthetic eukaryote. Such compartments have been made from a diverse group of amphiphilic vesicle forming molecules, including coacervates [7], polymer- or lipid-based water-in-oil droplets [8, 9] and water-in-water polymersomes [10]. The most frequently chosen compartment type are giant unilamellar vesicles (GUVs). Their key advantage lies in the use of lipids, which, as the building blocks of natural cell membranes, allow for the reconstitution of many cellular components without loss of functionality. GUVs are commonly produced by electroformation [11], or alternatively by gentle hydration [12, 13], microfluidic jetting [14], and solvent evaporation methods [15]. Unfortunately, these techniques often require specific buffers and lipid compositions that may be incompatible with specific cellular modules. The encapsulation efficiency is typically low, meaning that the molecularly crowded environment of a living cell cannot be mimicked efficiently.<\/p>\n
More recently, microfluidics has been used to produce GUVs on a chip by de-wetting of double-emulsion droplets (Figure 2) [16, 17]. Even mechanical on-chip division has been achieved [18]. The advantage of microfluidic methods is that GUVs can be produced at kilohertz rates with unprecedented control over the uniform compartment size. Moreover, the choice of membrane composition and buffer conditions is more flexible compared to the standard methods. Functional modules or reagents can be directly encapsulated in the aqueous inlet during the formation process of the GUVs. However after formation, the manipulability remains limited as GUVs are chemically and mechanically unstable [19]. This means that it is difficult to co-reconstitute reagents sequentially if they cannot be mixed together in one pot during compartment formation. Recently, Weiss and colleagues demonstrated a high-throughput, droplet-based microfluidic approach to generate stable, defined-size vesicles termed droplet-stabilized GUVs (dsGUVs) [20]. dsGUVs can be loaded sequentially with multiple different components or functional modules by means of picoinjection microfluidics [21] before being released from the oil phase and from the polymer shell into a physiological environment. Developments like these leave no doubt that microfluidics will increase the scope for complexity in the field of bottom-up synthetic biology [22, 23]. We highlight the applicability of such microfluidic units throughout this review (Box 2 and Figure 2).
\nBox 2<\/p>\n
+
\nBox 2
\nMicrofluidic Modules for Synthetic Biology
\nAt this point it seems likely that a synthetic eukaryote will be enclosed by a lipid membrane, as this approach allows for the straight-forward inclusion of natural building blocks. Moreover, this strategy will allow for the formation of a complex endomembrane system, the next step towards architectural mimicry of a eukaryotic cell.
\nEndomembrane System with Organelles
\nEukaryotic life is characterized by the coexistence of various internal membrane structures surrounding the nucleus and other organelles. Organized hierarchically, dedicated compartments take control of crucial functions including, but not limited to, nucleic acid production, material storage, and energy production. In this section, we first focus on processes to obtain synthetic multicompartment cells. We then showcase achievements towards synthetic cell nuclei and mitochondria as two key organelles and finally discuss strategies to obtain complex membrane morphologies beyond the archetypal spherical shape.<\/p>\n
Multicompartment Vesicles
\nSynthetic cells with multiple functional compartments represent a crucial first step towards the structural mimicry of eukaryotes. They offer a route towards higher-order functions by uncoupling enzymatic reactions, concentrating reagents, and separating incompatible cellular modules. Synthetic multicompartment vesicles, also referred to as multivesicular vesicles, nested vesicles, or vesosomes, can emerge from spontaneous or induced [24] endobudding of GUVs. They have also been formed by mimicking the natural process of endosymbiosis [25]. However, these methods cannot provide the desired control over number, cargo and membrane composition of the inner compartments.<\/p>\n
Overcoming these limitations, Deng and colleagues achieved precise control over compartment number and content in a high-throughput manner using a capillary-based microfluidics as illustrated in Figure 2A [26]. They also demonstrated the size-selective transfer of fluorescent dyes between inner and outer compartment by incorporating protein pores [26] \u2013 a first step towards regulating chemical and electrical communication between the compartments. However, the major drawback of this current technology is that the compartments cannot be modified or manipulated after their formation. This could potentially be addressed by inserting preformed internal compartments via microfluidic picoinjection unit as illustrated in Figure 2, or by adapting the picoinjection technology to water-in-water systems.<\/p>\n
Multicompartment systems have recently also been introduced into living cells, where they perform enzymatic cascade reactions [27]. Such developments open up a route towards smart synthetic cells capable of in vivo diagnostics and algorithmic release of hierarchically organized compounds. In the context of synthetic biology, internally structured vesicles are key to reverse-engineer the morphology and functionality of eukaryotic cells. They can serve as model systems to mimic endosymbiosis or molecular and supramolecular processes that occur in living cells. Yet, this ultimately requires strategies to organize the internal compartments. Here, the programmability of DNA provides interesting opportunities: single-stranded DNA has been covalently modified with hydrophobic moieties that self-assemble into lipid membranes. This way, lipid compartments tagged with cDNA sequences have been positioned in a programmable and reversible manner [28]. More generally, synthetic biology can capitalize on a pre-existing toolbox of functional units that were developed in the field of DNA nanotechnology over the past decades (Table 1, Figure 3, and Box 3). Progress towards synthetic cell nuclei and mitochondria as two key compartments of eukaryotes will be discussed in the following sections.<\/p>\n
Table 1DNA Nanotechnology-based Mimics of Cellular Components for Synthetic Cells
\nCellular component
\nDNA mimic and its function
\nIn\/on GUVs?
\nRefs
\nExosomes, transport vesicles
\nDNA capsules for stimuli-controlled release of cargo
\nNo
\n[30]
\nEpsin, clathrin
\nCurvature-imposing DNA structures for membrane bending
\nYes
\n[31, 32, 33]
\nTubulation of organelles
\nDNA-based scaffolds for complex reconfigurable membrane architectures
\nNo
\n[34, 35, 36]
\nCytoskeletal proteins
\nMembrane-bound DNA-based lattices for compartment stabilization
\nYes
\n[37]
\nRibosomes
\nDNA-based assemblers for synthesis of polymers with programmed sequence
\nNo
\n[38]
\nAntibodies
\nDNA aptamers for molecular recognition
\nYes
\n[39, 40]
\nIon channels, porins
\nDNA-based membrane pores for electrical and chemical communication between compartments
\nYes
\n[41, 42, 43]
\nScramblases
\nMembrane-spanning DNA constructs for transport of lipids between bilayer sheets
\nYes
\n[44]
\nSNARE proteins
\nMembrane-anchored DNA to mediate compartment fusion
\nYes
\n[45]
\nE-cadherins
\nDNA-based compartment linkers for reversible and programmable assembly of multicompartment systems
\nYes
\n[28]
\nActomyosin, microtubules, kinesin
\nDNA-based molecular walkers for programmable cargo transport
\nNo
\n[46, 47, 48]
\nLight-harvesting complexes
\nDNA origami platforms for rationally designed antenna structures
\nNo
\n[49]
\nView Table in HTML<\/p>\n
Box 3<\/p>\n
+
\nBox 3
\nDNA Nanotechnology for Synthetic Biology
\nCell Nucleus
\nOf all membrane-enclosed compartments, the nucleus is the defining part of the eukaryotic cell \u2013 giving the domain of life its name. It stores and organizes the genetic code, while making its information accessible for the production of proteins. Thus, the incorporation of a cell nucleus or its mimic is of special interest for synthetic eukaryotes.<\/p>\n
The simplest strategy is to encapsulate the functional nucleus of a living cell into a synthetic compartment. While the resulting hybrid may not be fully synthetic, this experiment led to an important insight: it revealed that the size of the mitotic spindle could be influenced by changing the compartment volume alone [50, 51]. However, control over the function of the cell nucleus is still limited due to the complexity of the eukaryotic genome. Therefore, Deng and colleagues recently presented the first simple artificial mimic of a cell nucleus within a lipid-based synthetic cell: by means of capillary-based microfluidics (Figure 2), they embedded a liposome containing an in vitro transcription mix into larger compartments [26]. In this system proteins were produced directly in the internal DNA-containing compartment. The highly challenging next step is to transfer RNA across the inner compartment membrane to achieve the spatial separation of transcription and translation which characterizes eukaryotes. This requires the use of a membrane pore that is large enough to allow for the passage of RNA, but impermeable to all precursors needed for the transcription process. In nature, the selective passage of RNA is achieved by the nuclear pore complex, which, until now, cannot be reconstituted into a synthetic system in its functional form.<\/p>\n
Large protein nanopores that remain open for extended periods of time are rare and often difficult to purify. Here, an artificial pore may be easier to obtain: a DNA origami nanopore that matches the electrical diameter of the nuclear pore complex has already been demonstrated [41], and single-stranded DNA has been translocated through DNA pores under an applied electrical field [42] (Table 1). Yet, current examples of DNA-based pores lack the sophisticated selectivity of the nuclear pore complex. Positioning peptides from the nuclear pore complex on a DNA origami scaffold as shown recently [52, 53] could be a promising approach. Circumventing the need for a pore, microfluidic picoinjection, or fusion technologies (Figure 2) could achieve the transfer of preformed mRNA into the synthetic compartment. Alternatively, the membrane of the synthetic nucleus could be made from a more porous material instead of lipids, like stimuli-responsive DNA-based capsules (Table 1) [30]. Also nucleocapsids could serve as mimics of a cell nucleus. Such capsids, capable of evolution, have recently been made from synthetic proteins [54]. Recently, Krinsky and colleagues demonstrated synthetic DNA-containing cells made of a single compartment capable of synthesizing therapeutic proteins inside tumors [55].<\/p>\n
Still, in vitro expression of one or a few proteins cannot compete with the complexity of a eukaryotic genome, where thousands of different proteins are produced in a genetically regulated manner. Using a top-down approach, minimal eukaryotic genomes have been designed and partially synthesized [56]. Smaller minimal prokaryotic genomes have even been booted in living cells [57, 58], but never in synthetic cells. While it is possible to create both, partially functional synthetic cell nuclei and fully functional semisynthetic genomes, putting the two together and booting a full genome inside a synthetic cell remains an unachieved and still distant goal.
\nMitochondria
\nEnergy generation is the key process to sustain life in an out-of-equilibrium state. In cellular systems, protons are pumped across a membrane to establish a proton gradient, which is then often transformed into the chemical energy currency ATP [59]. Maintenance and replication of complex internal membrane structures and large genomes requires an increased amount of ATP. It has been proposed that energy limitations in prokaryotes may constrain their complexity [60]. Under this scenario, the internalization of the energy generation, hence the acquisition of mitochondria, was the key step en route to the more complex eukaryotic cell plan. Autonomous synthetic eukaryotes will thus need a form of artificial mitochondria.<\/p>\n
A minimal system for ATP production requires an enzyme that can establish a proton gradient in combination with ATP synthase or a synthetic analog, which dissipates the energy from the proton gradient to produce ATP. The light-driven proton pump bacteriorhodopsin and the enzyme ATP synthase have successfully been co-reconstituted into small unilamellar vesicles [61] and polymersomes [62]. Instead of light, it is also possible to use the energy from the reduction of oxygen for ATP production by replacing bacteriorhodopsin with ubiquinol bo3 oxidase in small unilamellar vesicles [63, 64] and polymersomes [65]. Their co-reconstitution has also been achieved in cell-sized GUVs [66], where ATP synthase has been shown to induce nonequilibrium membrane fluctuation [67]. The next step is the encapsulation of such artificial mitochondria into a bigger compartment to mimic the architecture of a eukaryotic cell. Here, the microfluidic encapsulation or picoinjection of small vesicles into a large compartment or vesosomes (Figure 2) might be a promising strategy.<\/p>\n
Due to the unfavorable surface area to volume ratio, energy production across the external membrane is unlikely to sustain vital energy-intensive processes in eukaryotes \u2013 synthetic or natural. Natural mitochondria have a complex and folded inner membrane architecture with so-called cristae to provide additional space for the enzymes of the electron transport chain. Khalifat and colleagues observed the appearance of cristae-like invaginations in the presence of a local pH gradient, proposing a model to explain the membrane morphology of mitochondria [68]. Yet, not only mitochondria are characterized by their complex membrane architectures as described in the next section.
\nComplex Membrane Morphologies
\nEndocytic pits, filopodia, apoptotic blebs, or the endoplasmic reticulum (ER) are examples of dynamic function-related membrane structures in eukaryotes. In synthetic compartments, however, the energetically favorable spherical shape remains predominant. Cells achieve membrane deformations inter alia via specialized membrane-inserting proteins. Reconstitution of such membrane-bending proteins, like epsin, into synthetic compartments revealed the concentrations required for membrane bending [69] and the mechanisms by which intrinsically disordered proteins cause membrane tubulation [70]. Similarly, amphiphatic DNA-based constructs have been used as synthetic analogs to drive membrane tubulation [31] (Table 1). By inserting clathrin into GUVs, it has been shown that the balance between membrane elasticity and polymerization energy sets the shape of clathrin pits involved in endocytosis [71]. DNA nanotechnology, however, is currently the only strategy by which custom-designed, arbitrary, and reconfigurable lipid architectures can be obtained in a reproducible manner: a DNA template defines the shape of the lipid compartment and triggers the formation of a lipid bilayer on its surface via hydrophobic tags [35, 36]. Using this method, Zhang and colleagues recently demonstrated helical lipid tubes or ER-like structures that can be remodeled dynamically by reconfiguring the DNA template [34] \u2013 again highlighting the versatile applicability of DNA nanotechnology for synthetic cells. The encapsulation of such lipid architectures into larger compartments should be straightforward, for instance by means of microfluidic technologies as presented in Figure 2. Spherical and tubular lipid architectures have been released from their DNA shell by means of DNA-digesting enzymes [35, 36]. More complex shapes, however, are energetically unstable and have to be sustained via an internal or external cytoskeleton mimic. Approaches to obtain such a cytoskeleton are discussed in the next section. Nevertheless, it will still take time before the dynamic membrane architecture of a eukaryotic cell can be modeled and faithfully copied in a synthetic system. Therefore, it appears likely that the first synthetic eukaryote will predominantly rely on a spherical multicompartment architecture.
\nVersatile Cytoskeleton
\nAs a network of interlinking filaments extended throughout the cytoplasm, cytoskeletal elements share important roles in prokaryotes and eukaryotes, such as chromosome segregation and cytokinesis [72]. Cytoskeleton associated motor proteins for actin-based force generation and intracellular transport, however, are unique to eukaryotes and will be subject of this section.<\/p>\n
Actomyosin-Based Force Generation
\nFilamentous actin (F-actin) polymerizes into polarized filaments, which favor growth at one end and shrinkage at the other. This ATP-driven process allows for rapid actomyosin cytoskeletal changes that generate forces for processes like motility or endocytosis. Minimal actin cytoskeleton systems have been reconstituted mainly in bulk. These works provided important insights related to the biophysical process of actin cytoskeleton formation and its functions. Imposing confinement, contractile actomyosin rings have been demonstrated in water-in-oil droplets in the presence of bundling factors [73]. Such contractile rings initiate the division of many eukaryotic cells. In the presence of actin and a minimal set of actin-binding proteins, Liu and colleagues observed filopodium-like protrusions [74]. This means that the membrane alone can facilitate the transition of a branched actin network to a parallel array of actin filaments. The formation of such protrusions can be considered as the first step towards reconstituting protrusion-based cellular motility. In many cases, motility requires cells to adhere and to interact with the extracellular environment. Towards this end, reconstitution of surface receptors interlinking the extracellular matrix and the internal cytoskeleton in synthetic cells is a necessary step. To achieve substrate-specific adherence, functional integrins have been reconstituted into GUVs by means of microfluidic picoinjection [20] or by reconstitution during GUV electroformation [75]. The fact that no enrichment of integrins was observed in the adhesion patches [75] indicates the important contribution of the cytoskeleton to the formation of focal adhesions. This is underlined by the observations of Murrell and colleagues who reported cell-like spreading of a GUV with an actin cortex alone [76]. Obviously, the next key step would be to find a minimal set of components \u2013 natural or artificial \u2013 linking integrins to the actin cortex. The joint reconstitution of these components is unlikely to be achievable in a one-step reaction. A potential strategy could be to assemble integrin-GUVs first and to supply the linkers and actin in a subsequent step, for instance via microfluidic picoinjection or fusion units (Figure 2).<\/p>\n
The last step in the protrusion-based migration process is the myosin-based contraction of the actin network, combined with the detachment of the rear focal adhesions. Synthetic cells served as model systems to study how myosin builds tension in actin networks. Experiments reconstituting actin on the inside or on the outside of GUVs showed that cortex connectivity and membrane attachment govern the contraction outcome: cortices contract inward when weakly attached, whereas they contract towards the membrane when strongly attached [77]. Cortical flows and spontaneous symmetry breaking reminiscent of the initial polarization in embryo development was observed in actomyosin-loaded GUVs [78, 79] and in water-in-oil droplets [80]. While none of the systems described above show movement, it now seems to be an achievable goal. If the motility can be self-sustained via the internal production of ATP, as described in Mitochondria section, this would be a remarkable milestone towards autonomous synthetic cells. Progress in this direction will almost certainly rely on strategies to transfer the functional components step-by-step into a preformed compartment as demonstrated via microfluidics.
\nMicrotubules and Intracellular Transport
\nTogether with actin and intermediate filaments, microtubules form the eukaryotic cytoskeleton. They are capable of generating force via directional growth and serve as tracks for motor proteins, which carry organelles and other components to their target location. Compelling evidence exists that microtubules and molecular motors of the dynamin and kinesin families are involved in the tubulation of organelles, thereby establishing the architecture of eukaryotic cells.<\/p>\n
It has been shown that a minimal system consisting of GUVs and externally supplied microtubules and kinesin can produce membrane networks in the presence of ATP and GTP \u2212 without the aid of other proteins [81]. Increasing the level of complexity one step further, a basic minimal endocytosis module was reconstituted: the addition of dynamin caused membrane fission and vesicle release [82]. It should be noted, however, that all reagents were not encapsulated within the GUV but added externally. Their reconstitution inside a lipid compartment should be straightforward using microfluidic encapsulation or picoinjection (Figure 2). This could be a strategy for the autonomous creation of a multicompartment system. As a first step, tubulin has already been polymerized inside microfluidic droplets [20, 83]. Remarkably, Sanchez and colleagues demonstrated spontaneous motion of droplets loaded with microtubules and kinesin, likely caused by cytoplasmic streaming [83]. Juniper and colleagues presented a robust microfluidic system to study motor protein and microtubule self-organization in polymer-stabilized droplets of well-defined size. An important outcome of this study was that confinement can impose a novel pathway for microtubule aster formation via the constriction of an initially spherical motor-microtubule network. The observed mechanism illustrates the close relationship between confinement, network contraction, and aster formation [84]. With the successful reconstitution of actin contractile rings [73] and microtubule asters, the controlled division of synthetic cells may be an achievable goal. It will be necessary to find suitable linkers between the cytoskeletal components and to combine the system with an ATP-generating module.<\/p>\n
Deviating from natural systems, DNA-based motors that walk along a track are the most promising candidates to recapitulate intracellular transport in a purely synthetic manner. In these systems, movement is fuelled by the hybridization and subsequent hydrolysis of DNA base pairs between the DNA-based motor and its track. Long-range transport with rates up to 2\u2005\u03bcm\/min [85], as well as programmable navigation through branched track networks [86] and cargo sorting [46], have been demonstrated. Recently, regulatory inputs in the form of DNA strands were provided to the motor sequentially by means of microfluidics increasing its performance [47]. All these systems have not yet been encapsulated into lipid compartments, although this step should be well within reach.<\/p>\n
Recently, a DNA lattice has been absorbed onto the inner compartment membrane of a GUV [37]. So far, the only function of this synthetic cytoskeleton is to stabilize the synthetic cell. In principle, however, it could serve as a track for DNA-based motors and provide anchoring points or linkers for other modules of synthetic cells.
\nConcluding Remarks
\nIn the past two decades, bottom-up synthetic biology has successfully reconstituted various phenomena occurring in living systems. Emphasis is now being put on strategies to integrate functional modules into multifunctional systems. Until recently, the lack of technologies for the sequential assembly and manipulation of synthetic cells was limiting the progress. This hurdle has largely been overcome thanks the introduction of precision technologies, like microfluidics, into the field. Previously developed functional modules can now, in principle, be assembled in a step-by-step manner with unprecedented control. These functional modules, however, may lose their activity when recombined due to undesired chemical or physical interactions or incompatible buffer conditions (see Outstanding Questions). Here, mimicking the architecture of eukaryotes with their multiple compartments and segregated reaction pathways holds the key to success. Engineering sophisticated membrane pores will then be necessary to allow for communication and selective exchange of reagents.<\/p>\n
Some cellular modules, however, will remain difficult to reconstitute. In this case, artificial mimics may be an adequate solution. Especially, the field of DNA nanotechnology offers new opportunities: as highlighted in this review, DNA-based constructs have successfully been used to program the assembly of cellular components and to achieve functionality that is normally provided by proteins. Additionally, the integration of synthetic designer proteins and computational tools for their structure prediction will increase the versatility of synthetic cells.<\/p>\n
Moving away from naturally occurring building blocks is conceptually interesting and offers a route towards truly synthetic systems, which has profound implications for the definition of life in itself. In some cases, however, it will remain difficult to match the efficiency and sophistication of engineering solutions offered by nature. Therefore, a combination approach using both natural and synthetic building blocks will likely be the best strategy. It will also be enriching to recombine bottom-up and top-down approaches to synthetic biology.<\/p>\n
In the coming years, the integration of evolution into the conceptual toolbox of bottom-up synthetic biology will lead to exciting developments. So far, there is no study that has convincingly demonstrated open-ended evolution in a synthetic system. Additionally, a long-term goal is to integrate synthetic cells into a compartment hierarchy analogous to the organelle \u2013 cell \u2013 tissue \u2013 organ structure of multicellular systems. Here, it will be powerful to combine algorithmic self-assembly facilitated by DNA nanotechnology with microfluidic bioprinting of synthetic cells. After all, it was ultimately the emergence of multicellularity that gave rise to the mesmerizing diversity of life on Earth. We may thus be looking forward to witness future developments in this emerging field, when scientific curiosity continues to follow the intrinsic motivation of human endeavor \u2013 to discover the secret of life. Just like life will keep converging towards the best solutions, so will, no doubt, the myriad of approaches to synthetic biology.<\/p>\n","protected":false},"excerpt":{"rendered":"
Bottom-up synthetic biology thrives in reverse-engineering a particular biological function using a minimal set of molecular components, like purified proteins. Recently, precision technologies, like microfluidics, have been used to recombine functional modules towards multifunctional synthetic cells. Synthetic biology can capitalize on a variety of pre-existing on-chip functions, which greatly increases the scope for complexity in […]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","nova_meta_subtitle":"","footnotes":""},"categories":[5572],"tags":[14438,14439,12417],"supplier":[11310],"class_list":["post-52240","post","type-post","status-publish","format-standard","hentry","category-bio-based","tag-biology","tag-dna","tag-proteins","supplier-cell-magazine"],"_links":{"self":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/52240","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/comments?post=52240"}],"version-history":[{"count":0,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/52240\/revisions"}],"wp:attachment":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/media?parent=52240"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/categories?post=52240"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/tags?post=52240"},{"taxonomy":"supplier","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/supplier?post=52240"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}