Biology subjects

Modzelewski, A. J.

Publications and source records attributed to Modzelewski, A. J..

4 recordsLinked to original sources

bioRxiv2026

An Intronic SINE at Pou5f1 Links Hormone Signaling to Blastocyst Hatching

Before implantation, mammalian embryos must escape from the zona pellucida, a protective glycoprotein coat that surrounds the blastocyst. This process, known as hatching, is essential for uterine attachment and has been viewed largely as a mechanical consequence of blastocyst expansion and zona weakening. Whether hatching is actively timed by embryo-intrinsic gene regulation remains unclear. Here we show that timely hatching of mouse embryos requires signal-responsive repression of Pou5f1/OCT4 in the trophectoderm by a single intronic B2 short interspersed nuclear element. Deleting this element preserves blastocyst formation and stem-cell competence, but disrupts trophectodermal OCT4 repression, delays zona escape, causes hatching-uterine receptivity mismatch, perturbs implantation-site organization and reduces peri-implantation fitness. CRISPR activation screening, siRNA and pharmacological perturbation, and defined progesterone/estradiol/EGF culture conditions identify an ESRRA-linked endocrine/growth-factor response that requires the B2 element to consolidate trophectoderm maturation. Comparative analyses further show that young intronic SINEs are enriched in developmental gene programs, whereas human POU5F1 intronic Alu elements exhibit genetic constraint and repressive potential. These findings identify intronic SINEs as molecular entry points that couple extracellular cues to lineage-restricted transcriptional control and morphogenic transition.

developmental biology↗

bioRxiv2021

A species-specific retrotransposon drives a conserved Cdk2ap1 isoform essential for preimplantation development

Retrotransposons mediate gene regulation in multiple developmental and pathological processes. Here, we characterized the transient retrotransposon induction in preimplantation development of eight mammalian species. While species-specific in sequences, induced retrotransposons exhibit a similar preimplantation profile, conferring gene regulatory activities particularly through LTR retrotransposon promoters. We investigated a mouse-specific MT2B2 retrotransposon promoter, which generates an N-terminally truncated, preimplantation-specific Cdk2ap1{Delta}N isoform to promote cell proliferation. Cdk2ap1{Delta}N functionally contrasts to the canonical Cdk2ap1, which represses cell proliferation and peaks in mid-gestation stage. The mouse-specific MT2B2 element is developmentally essential, as its deletion abolishes Cdk2ap1{Delta}N, reduces cell proliferation and impairs embryo implantation. Intriguingly, Cdk2ap1{Delta}N is evolutionarily conserved across mammals, driven by species-specific promoters. The distinct preimplantation Cdk2ap1{Delta}N expression across different mammalian species correlates with their different duration in preimplantation development. Hence, species-specific transposon promoters can yield evolutionarily conserved, alternative protein isoforms, bestowing them with new functions and species-specific expression to govern essential biological divergence. One Sentence SummaryIn mammalian preimplantation embryos, retrotransposon promoters generate conserved gene isoforms, confer species-specific expression, and perform essential developmental functions.

developmental biology↗

bioRxiv2020

An unusual MHC molecule generates protective CD8+ T cell responses to chronic infection

The CD8+ T cell response to the intracellular parasite Toxoplasma gondii varies dramatically between mouse strains, resulting in differences in control of the parasite. Protection in BALB/c mice can be attributed to an unusually strong and protective MHC-1 Ld-restricted CD8+ T cell response directed against a peptide derived from the parasite antigen GRA6. The MHC-1 Ld molecule has limited peptide binding compared to conventional MHC molecules such as Kb or Db, which correlates with polymorphisms associated with "elite control" of HIV in humans. To investigate the link between the unusual MHC-1 molecule Ld and the generation of "elite controller" CD8+ T cell responses, we compared the GRA6-Ld specific T cell response to the well-studied OVA-Kb specific response, and demonstrated that GRA6-Ld specific T cells are significantly more protective and resistant to exhaustion in chronic T. gondii infection. To further investigate the connection between limited peptide presentation and robust T cell responses, we used CRISPR/Cas9 to generate mice with a point mutation (W97R) in the peptide-binding groove of Ld that results in broader peptide binding. We investigated the effect of this Ld W97R mutation on another robust Ld-restricted response against the IE1 peptide during Murine Cytomegalovirus (MCMV) infection. This mutation leads to an increase in exhaustion markers in the IE1-Ld specific CD8+ T cell response. Our results indicate that limited peptide binding by MHC-1 Ld correlates with the development of robust and protective CD8+ T cell responses that may avoid exhaustion during chronic infection.

immunology↗

bioRxiv2018

Single-embryo and single-blastomere immunoblotting reports protein expression heterogeneity in early-stage preimplantation embryos

Understanding how a zygote develops from a single cell into a multicellular organism has benefitted from single-cell tools, including RNA sequencing (RNA-Seq) and immunofluorescence (IF). However, scrutinizing inter- and intra-embryonic phenotypic variation is hindered by two fundamental limitations; the loose correlation between transcription and translation and the cross-reactivity of immunoreagents. To address these challenges, we describe a high-specificity microfluidic immunoblot optimized to quantify protein expression from all stages of mouse preimplantation development. Despite limited availability of isoform-specific immunoreagents, the immunoblot resolves inter-embryonic heterogeneity of embryo-specific isoforms (i.e., DICER-1). We observed significantly higher DICER-1 isoform expression in oocytes when compared to two-cell embryos, and further find that protein expression levels follow the same trend as mRNA for both the full-length and truncated DICER-1 isoforms. At the morula stage, we assayed both whole and disaggregated embryos for loading controls ({beta}-tubulin, GAPDH) and markers that regulate cell fate decisions (CDX-2, SOX-2). In disaggregated morula, we found that cell volume showed positive, linear correlation with expression of {beta}-tubulin and SOX-2. In dissociated two-cell and four-cell blastomeres, we detect significant inter-blastomeric variation in GADD45a expression, corroborating suspected cellular heterogeneity even in the earliest multicellular stage of preimplantation embryos. As RNA-Seq and other transcript-centric approaches continue to further probe preimplantation development, the demand for companion protein-based techniques rises. The reported microfluidic immunoblot serves as an essential tool for understanding mammalian development by providing high-specificity and direct measurements of protein targets at single-embryo and single-blastomere resolution.

bioengineering↗