Biology subjects

Sekulovski, N.

Publications and source records attributed to Sekulovski, N..

4 recordsLinked to original sources

bioRxiv2026

High resolution spatial transcriptomic and proteomic profiling of early primate gastrulation in utero

Early gastrulation represents a key stage in which several embryonic and extra-embryonic lineages are formed in the primitive streak to support embryonic development. However, very little is known about lineage specification events in the early primate gastrula. To gain molecular insights into mechanisms that organize this stage of primate development, we performed high-resolution spatial transcript and protein expression profiling of five sagittal sections from a cynomolgus macaque embryo at Carnegie Stage 6b, an early gastrulation stage. We established a molecular map of six major cell populations: the epiblast, primitive streak, amnion, endoderm, mesoderm, and primordial germ cells. We also uncovered a variety of lineage subtypes, as well as important signaling and transcriptional networks. In particular, we show that canonical WNT signaling is a driver of amnion fate progression. Together, this study provides a unique multiomic resource of an early primate gastrula with complete spatial information for future investigations.

developmental biology↗

bioRxiv2025

The endo-lysosomal system drives lumen formation in a human epiblast model

The formation of a central lumen in the epiblast is a critical step that occurs during implantation in the human embryo. Lumen formation is accompanied by highly dynamic and complex cargo trafficking in the endo-lysosomal system. However, our understanding of key players and machineries that control this critical trafficking process remains incomplete in the context of epiblast development. Here, we explored endo-lysosomal dynamics that are associated with the generation of the apicosome, the earliest stage of lumen formation in a model of human epiblast development based on human pluripotent stem cells. We uncovered a hybrid early/late endosome compartment as well as a previously unrecognized dynamics of late endosome and lysosome compartments in trafficking podocalyxin (PODXL), a sialomucin glycoprotein that helps to establish and maintain the open lumen, during apicosome formation. To gain molecular insight into these unique hybrid endosome and late endosome/lysosome machineries in PODXL traffic, we used APEX2-based spatial proteomics to identify PODXL-proximity partners during apicosome formation, and identified RAB35, a Rab small GTPase known to control PODXL traffic as well as early and late endosome dynamics, as a key player in controlling apicosome formation. Our results suggest that RAB35 limits excess apicosome formation by promoting the early to late endosome transition as well as lysosome formation, which help to reduce PODXL to a level necessary for single apicosome formation. Overall, this study reveals novel endo-lysosomal mechanisms that contribute to apical membrane morphogenesis in a human model of epiblast formation.

developmental biology↗

bioRxiv2023

Identification of amnion progenitor-like cells at the amnion-epiblast boundary in the primate peri-gastrula

Amniogenesis is triggered in a collection of pluripotent epiblast cells as the human embryo implants. To gain insights into the critical but poorly understood transcriptional machinery governing amnion fate determination, we examined the evolving transcriptome of a developing human pluripotent stem cell-derived amnion model at the single cell level. This analysis revealed several continuous amniotic fate progressing states with state-specific markers, which include a previously unrecognized CLDN10+ amnion progenitor state. Strikingly, we found that expression of CLDN10 is restricted to the amnion-epiblast boundary region in the human post-implantation amniotic sac model as well as in a peri-gastrula cynomolgus macaque embryo, bolstering the growing notion that, at this stage, the amnion-epiblast boundary is a site of active amniogenesis. Bioinformatic analysis of published primate peri-gastrula single cell sequencing data further confirmed that CLDN10 is expressed in cells progressing to amnion. Additionally, our loss of function analysis shows that CLDN10 promotes amniotic but suppresses primordial germ cell-like fate. Overall, this study presents a comprehensive amniogenic single cell transcriptomic resource and identifies a previously unrecognized CLDN10+ amnion progenitor population at the amnion-epiblast boundary of the primate peri-gastrula.

developmental biology↗

bioRxiv2023

Temporally resolved early BMP-driven transcriptional cascade during human amnion specification

Amniogenesis, a process critical for continuation of healthy pregnancy, is triggered in a collection of pluripotent epiblast cells as the human embryo implants. Previous studies have established that BMP signaling is a major driver of this lineage specifying process, but the downstream BMP-dependent transcriptional networks that lead to successful amniogenesis remain to be identified. This is, in part, due to the current lack of a robust and reproducible model system that enables mechanistic investigations exclusively into amniogenesis. Here, we developed an improved model of early amnion specification, using a human pluripotent stem cell-based platform in which the activation of BMP signaling is controlled and synchronous. Uniform amniogenesis is seen within 48 hours after BMP activation, and the resulting cells share transcriptomic characteristics with amnion cells of a gastrulating human embryo. Using detailed time-course transcriptomic analyses, we established a previously uncharacterized BMP-dependent amniotic transcriptional cascade, and identified markers that represent five distinct stages of amnion fate specification; the expression of selected markers was validated in early post-implantation macaque embryos. Moreover, a cohort of factors that could potentially control specific stages of amniogenesis was identified, including the transcription factor TFAP2A. Functionally, we determined that, once amniogenesis is triggered by the BMP pathway, TFAP2A controls the progression of amniogenesis. This work presents a temporally resolved transcriptomic resource for several previously uncharacterized amniogenesis states and demonstrates a critical intermediate role for TFAP2A during amnion fate specification.

developmental biology↗