Biology subjects

Morash, M.

Publications and source records attributed to Morash, M..

3 recordsLinked to original sources

bioRxiv2025

Intestinal enteroendocrine cell subtype differentiation and hormone production in zebrafish

Enteroendocrine cells (EECs) are rare sensory cells in the intestinal epithelium that coordinate digestive physiology by secreting a diverse repertoire of peptide hormones. These hormones are the main effectors of EEC function, and their characterization requires direct observation by mass spectrometry due to the specialized protein cleavage and posttranslational modifications that yield their mature forms. Based on the distinct subset of hormones they predominantly secrete, EECs can be categorized into subtypes. How each EEC subtype is specified, however, remains poorly understood. Here we describe EEC subtype differentiation and hormone production in the zebrafish. Using single-cell RNA sequencing data, we identified EEC progenitors and six EEC subtypes in zebrafish and revealed that their expression profiles are consistent across larval and adult stages. Mass spectrometry analysis of isolated zebrafish EECs identified highly processed peptides derived from 18 of 21 hormone coding genes expressed by EECs, yielding a catalog of >400 unique EEC hormone peptides. We assembled reporters for zebrafish EEC subtypes to test the lineage relationships between EEC subtypes and the EEC progenitor population, which expresses neurogenin3. Despite its essential role in mammalian EEC differentiation, we found that selective cytotoxic ablation of neurogenin3+ cells in zebrafish only reduced a subset of EEC subtypes. Finally, we discovered that selective ablation of ghrelin+ EECs reduced a different subset of EEC subtypes, together suggesting that neurogenin3+ and ghrelin+ cells serve as distinct precursors for separate EEC subtypes. We anticipate these observations and resources will facilitate future studies in the zebrafish to discern the developmental biology, physiology, and endocrinology of EEC subtypes.

developmental biology↗

bioRxiv2022

Pla2g12b is Essential for Expansion of Nascent Lipoprotein Particles

SUMMARYTriglyceride-rich lipoproteins (TRLs) are micelle-like particles that enable efficient transport of lipids throughout the bloodstream, but also promote atherosclerotic cardiovascular disease. Despite this central relevance to cardiovascular disease, very little is known about how lipids are loaded onto nascent TRLs prior to secretion. Here we show that Pla2g12b, a gene with no previously described function, concentrates components of the TRL biogenesis machinery along the ER membrane to ensure efficient delivery of lipids to nascent TRLs. We find that the lipid-poor TRLs secreted in PLA2G12B-/- mice and zebrafish support surprisingly normal growth and physiology while conferring profound resistance to atherosclerosis, and demonstrate that these same processes are conserved in human cells. Together these findings shed new light on the poorly understood process of TRL expansion, ascribe function to the previously uncharacterized gene Pla2g12b, and reveal a promising new strategy to remodel serum lipoproteins to prevent cardiovascular disease.

cell biology↗

bioRxiv2020

Mutation of NEKL-4/NEK10 and TTLL genes opposes loss of the CCPP-1 deglutamylase and prevents neuronal ciliary degeneration

Ciliary microtubules are subject to post-translational modifications that act as a "Tubulin Code" to regulate motor traffic, binding proteins and stability. In humans, loss of CCP1, a cytosolic carboxypeptidase and tubulin deglutamylating enzyme, causes infantile-onset neurodegeneration. In C. elegans, mutations in ccpp-1, the homolog of CCP1, result in progressive degeneration of neuronal cilia and loss of neuronal function. To identify genes that regulate microtubule glutamylation and ciliary integrity, we performed a forward genetic screen for suppressors of ciliary degeneration in ccpp-1 mutants. We isolated the ttll-5(my38) suppressor, a mutation in the tubulin tyrosine ligase-like glutamylase gene. We show that mutation in ttll-4, ttll-5, or ttll-11 gene suppressed the hyperglutamylation-induced loss of microtubules and kinesin-2 mislocalization in ccpp-1 cilia. We also identified the nekl-4(my31) suppressor, an allele affecting the NIMA (Never in Mitosis A)-related kinase NEKL-4/NEK10. In humans, NEK10 mutation causes bronchiectasis, an airway and mucociliary transport disorder caused by defective motile cilia. C. elegans NEKL-4 does not localize to cilia yet plays a role in regulating axonemal microtubule stability. This work defines a pathway in which glutamylation, a component of the Tubulin Code, is written by TTLL-4, TTLL-5, and TTLL-11; is erased by CCPP-1; is read by ciliary kinesins; and its downstream effects are modulated by NEKL-4 activity. Identification of regulators of microtubule glutamylation in diverse cellular contexts is important to the development of effective therapies for disorders characterized by changes in microtubule glutamylation. By identifying C. elegans genes important for neuronal and ciliary stability, our work may inform research into human ciliopathies and neurodegenerative diseases.

genetics↗