Biology subjects

Sarasamma, S.

Publications and source records attributed to Sarasamma, S..

3 recordsLinked to original sources

bioRxiv2026

A germline-specific reporter reveals conserved primordial germ cell developmental dynamics between jawless and jawed fish species

Primordial germ cells (PGCs) are the stem cell lineage responsible for transmitting genetic information across generations and are therefore central to studies of germline development, reproduction, and evolution. However, a lack of molecular tools in jawless vertebrates such as lampreys and hagfish has limited comparative insights into the evolutionary origins of vertebrate germline cells. Here, we report the development of the first germline-specific reporter (GSR) in the sea lamprey (Petromyzon marinus), Tg(piwil1: egfp-UTRnanos1), a piwil1-based germline reporter that is driven by the sea lamprey piwil1 regulatory region that directs Green Fluorescent Protein (GFP) expression in early PGCs. Promoter activity was validated by robust GFP expression in PGCs of zebrafish embryos co-injected with Tol2 transposase mRNA. Injection of the construct into sea lamprey embryos resulted in early, persistent, and gonad-localized GFP-positive cells. These results demonstrate stable germline-specific transgene expression in a jawless vertebrate and suggest deep evolutionary conservation of germline regulatory mechanisms between jawless and jawed vertebrates. Furthermore, the piwil1-based germline reporter line enabled lifetime visualization of zebrafish germline cells, revealing that increased PGC abundance during embryogenesis biases toward female sexual differentiation. Together, this study establishes the first GSR system in a jawless vertebrate and provides a useful platform for investigating germline biology and vertebrate germline evolution.

developmental biology↗

bioRxiv2026

Gonadal PIP-seq reveals genes involved in germ cell development and sexual differentiation in sea lamprey ( Petromyzon marinus )

Vertebrate sex determination is highly diverse, with distinct mechanisms that have evolved repeatedly and independently across phylogeny. The sea lamprey (Petromyzon marinus) is an extant jawless vertebrate that remains sexually labile during its larval stage that lasts around 3-20 years. Their gonad contains bipotential, female, and male germ cells before metamorphosis. To examine the genetic programs in germ cells at different developmental stages, we profiled transcriptomes of dissociated gonadal cells from larvae and recently metamorphosed juvenile (transformers, sex-determined) using fluorescence-activated cell sorting (BD FACS Aria IIu) and PIPseqTM (Fluent BioSciences/Illumina). 66,676 cells were sequenced and classified into 19 cell clusters according to their gene expression profiles. Primordial germ cells differentially expressed genes encoding various heat-shock proteins, hormones, growth factors, and their receptors, and proteins sensitive to iron, nitrogen starvation, sugar and lipid metabolisms, and oxidative stress, providing possible links between environmental factors, cellular functions, and cell fate determinants. Germ cells in larvae had enriched expression of genes involved in DNA replication, transcription, translation, apoptosis, autophagy, cell cycle, cell differentiation, cell adhesion and migration, cell survival, chromatin remodeling, and proliferation. Specifically, female germ cells differentially expressed various transcript isoforms of AEP1, CUZD1, S100A1, and ZP genes, whereas male germ cells differentially expressed BOLL and PIWIL1. Pseudotime trajectory and Gene Ontology (GO) analysis revealed that genes with changing expressions along the female differentiation pathway were involved in binding of sperm to zona pellucida, egg coat formation, prevention of polyspermy and positive regulation of acrosome reaction. On the other hand, genes with changing expressions along the male differentiation pathway were involved in ribosome assembly and translation. Several WNT5 transcripts were differentially expressed in germ cells or somatic cells. Our results suggest that sea lamprey sex determination and sexual differentiation likely involve the coordinated action of numerous genes that interact with various environmental factors and regulate germ cell specification and development.

Developmental Biology↗

bioRxiv2026

Zebrafish knockout models of atxn1a, atxn1b, and atxn1l reveal distinct and shared phenotypic and transcriptomic alterations

Spinocerebellar ataxia type 1 (SCA1) is a progressive neurodegenerative disorder caused by polyglutamine expansion in ATXN1, yet the normal physiological roles of ATXN1 and its paralog ATXN1L remain incompletely understood. To define these roles, we generated the first zebrafish knockouts (KOs) of the three ataxin-1 family genes, atxn1a, atxn1b, and atxn1l, using CRISPR/Cas9. These mutants reveal distinct and shared developmental, behavioral, and transcriptomic alterations. All KOs showed reduced early survival and mild larval growth deficits, indicating essential developmental functions. Behavioral assays revealed distinct paralog-specific effects: atxn1a KO larvae exhibited a unique light-dependent locomotor deficit, whereas atxn1b and atxn1l KOs displayed global hypoactivity. Adult behavioral assessment revealed a gradient of phenotypic severity: atxn1a KOs displayed the earliest and most pronounced alterations in vertical tank exploration and the greatest impairment in swim-tunnel performance, followed by atxn1b and then atxn1l mutants. To define molecular mechanisms underlying these phenotypes, we performed RNA-seq at 5 days post-fertilization and identified unique and shared differentially expressed genes across the three KO lines. Shared transcriptomic signatures highlighted suppression of leukotriene-biosynthetic pathways and diminished innate-immune pathways; suggesting that ATXN1-family genes influence neuroimmune signaling during early development. Weighted gene co-expression network analysis identified distinct KO-associated gene modules, including a phototransduction-enriched module strongly correlated with atxn1a KO status, offering a mechanistic link to its light-dependent locomotor phenotype. Together, these findings establish a comprehensive assessment of zebrafish models that reveal both shared core functions and specialized roles of ATXN1-family genes in development, neuroimmune regulation, sensorimotor behavior, and retinal signaling.

neuroscience↗