Molinuevo, R. | bioRxiv Science

bioRxiv2023

Nuclear VANGL2 Inhibits Lactogenic Differentiation

Planar cell polarity (PCP) proteins coordinate tissue morphogenesis by governing cell patterning and polarity. Asymmetrically localized on the plasma membrane of cells, PCP proteins are also trafficked by endocytosis, suggesting they may have intracellular functions that are dependent or independent of their extracellular role, but whether these functions extend to transcriptional control remains unknown. Here, we show the nuclear localization of transmembrane, PCP protein, VANGL2, in undifferentiated, but not differentiated, HC11 cells, which serve as a model for mammary lactogenic differentiation. Loss of Vangl2 function results in upregulation of pathways related to STAT5 signaling. We identify DNA binding sites and a nuclear localization signal in VANGL2, and use CUT&RUN to demonstrate direct binding of VANGL2 to specific DNA binding motifs, including one in the Stat5a promoter. Knockdown (KD) of Vangl2 in HC11 cells and primary mammary organoids results in upregulation of Stat5a, Ccnd1 and Csn2, larger acini and organoids, and precocious differentiation; phenotypes rescued by overexpression of Vangl2, but not Vangl2{Delta}NLS. Together, these results advance a paradigm whereby PCP proteins coordinate tissue morphogenesis by keeping transcriptional programs governing differentiation in check.

cell biology↗

bioRxiv2022

Subfunctionalized expression drives evolutionary retention of ribosomal protein paralogs in vertebrates

The formation of paralogs through gene duplication is a core evolutionary process. For paralogs that encode components of protein complexes such as the ribosome, a central question is whether they encode functionally distinct proteins, or whether they exist to maintain appropriate total expression of equivalent proteins. Here, we systematically tested evolutionary models of paralog function using the mammalian ribosomal protein paralogs eS27 (Rps27) and eS27L (Rps27l) as a case study. We first showed that eS27 and eS27L have inversely correlated mRNA abundance across cell types, with the highest eS27 in lymphocytes and the highest eS27L in mammary alveolar cells and hepatocytes. By endogenously tagging the eS27 and eS27L proteins, we demonstrated that eS27- and eS27L- ribosomes associate preferentially with different transcripts. Furthermore, we generated murine eS27 and eS27L loss-of-function alleles that are homozygous lethal at different developmental stages. However, strikingly, we found that expressing eS27 protein from the endogenous eS27L locus, or vice versa, completely rescues loss-of-function lethality and yields mice with no detectable deficits. Together, these findings suggest that eS27 and eS27L are evolutionarily retained because their subfunctionalized expression patterns render both genes necessary to achieve the requisite total expression of two equivalent proteins across cell types. Our work represents the most in-depth characterization of a mammalian ribosomal protein paralog to date and highlights the importance of considering both protein function and expression when investigating paralogs.

genetics↗