Biology subjects

Smela, M. P.

Publications and source records attributed to Smela, M. P..

3 recordsLinked to original sources

bioRxiv2023

RNA-catalyzed RNA Ligation within Prebiotically Plausible Model Protocells

Demonstrating RNA catalysis within prebiotically relevant models of primordial cells (protocells) remains a challenge in Origins of life research. Fatty acid vesicles encapsulating genomic and catalytic RNAs (ribozymes) are attractive models for protocells; however, RNA catalysis has largely been incompatible with fatty acid vesicles due to their instability in the presence of Mg2+ at concentrations required for ribozyme function. Here, we report a ribozyme that catalyzes template-directed RNA ligation at low Mg2+ concentrations and thus remains active within stable vesicles. Ribose and adenine, both prebiotically relevant molecules, were found to greatly reduce Mg2+-induced RNA leakage from vesicles. When we co-encapsulated the ribozyme, substrate, and template within fatty acid vesicles, we observed efficient RNA-catalyzed RNA ligation upon subsequent addition of Mg2+. Our work shows that RNA-catalyzed RNA assembly can occur efficiently within prebiotically plausible fatty acid vesicles and represents a step toward the replication of primordial genomes within self-replicating protocells.

biochemistry↗

bioRxiv2022

Efficient Human Germ Cell Specification from Stem Cells via Combinatorial Expression of Transcription Factors

The generation of germline cell types from human induced pluripotent stem cells (hiPSCs) represents a key milestone toward in vitro gametogenesis, which has the potential to transform reproductive modeling and medicine. Methods to recapitulate advanced germline cell specification in vitro have relied on extensive, long term culture methods, the most notable of which is a four-month culture protocol employing xenogeneic reconstituted ovaries with mouse embryonic ovarian somatic cells. Recently, transcription factor (TF)-based methods have demonstrated the feasibility of exogenous factor expression to directly differentiate hiPSCs into cell types of interest, including various ovarian cell types. The protocols leveraged in these studies, however, utilize more local methods of factor selection, such as basic differential gene expression analysis, and lower-throughput screening strategies via iterative testing of a small set of TFs. In this work, we integrate our recently-described graph theory pipeline and highly-parallelized screening protocols to globally identify and screen 46 oogenesis-regulating TFs for their role in human germline formation. We identify ZNF281, LHX8, SOHLH1, ZGLP1, and ANHX whose combinatorial overexpression drives DDX4+ induced oogonia-like cell (iOLC) formation from hiPSCs. In contrast to previous methods, our protocol employs a simple four-day, feeder-free monolayer culture condition. We additionally demonstrate a method of post-isolation, feeder-free expansion of DDX4+ iOLCs that shows retained cell identity in vitro. We additionally identify DLX5, HHEX, and FIGLA whose individual overexpression enhances hPGCLC formation from hiPSCs. We characterize these TF-based iOLCs and hPGCLCs via gene and protein expression analyses and demonstrate their broad similarity to in vivo and in vitro-derived oogonia and primordial germ cells. Together, these results identify new regulatory factors that enhance in vitro human germ cell specification and further establish unique computational and experimental tools for human in vitro oogenesis research.

developmental biology↗

bioRxiv2022

Directed Differentiation of Human iPSCs to Functional Ovarian Granulosa-Like Cells via Transcription Factor Overexpression

An in vitro model of human ovarian follicles would greatly benefit the study of female reproduction. Ovarian development requires the combination of germ cells and their supporting somatic cells, known as granulosa cells. Whereas efficient protocols exist for generating human primordial germ cell-like cells (hPGCLCs) from human iPSCs, a method of generating granulosa cells has been elusive. Here we report that simultaneous overexpression of two transcription factors (TFs) can direct the differentiation of human iPSCs to granulosa-like cells. We elucidate the regulatory effects of several granulosa-related TFs, and establish that overexpression of NR5A1 and either RUNX1 or RUNX2 is necessary and sufficient to generate granulosa-like cells. Our granulosa-like cells form ovary-like organoids (ovaroids) when aggregated with hPGCLCs, and recapitulate key ovarian phenotypes including support of germ cell maturation, follicle formation, and steroidogenesis. This model system will provide unique opportunities for studying human ovarian biology, and may enable the development of therapies for female reproductive health.

developmental biology↗