AUTHOR=Tonelli Francesca , Leoni Laura , Daponte Valentina , Gioia Roberta , Cotti Silvia , Fiedler Imke A. K. , Larianova Daria , Willaert Andy , Coucke Paul J. , Villani Simona , Busse Björn , Besio Roberta , Rossi Antonio , Witten P. Eckhard , Forlino Antonella 

TITLE=Zebrafish Tric-b is required for skeletal development and bone cells differentiation

JOURNAL=Frontiers in Endocrinology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2023.1002914

DOI=10.3389/fendo.2023.1002914

ISSN=1664-2392

ABSTRACT=<sec><title>Introduction</title><p>Trimeric intracellular potassium channels TRIC-A and -B are endoplasmic reticulum (ER) integral membrane proteins, involved in the regulation of calcium release mediated by ryanodine (RyRs) and inositol 1,4,5-trisphosphate (IP<sub>3</sub>Rs) receptors, respectively. While TRIC-A is mainly expressed in excitable cells, TRIC-B is ubiquitously distributed at moderate level. TRIC-B deficiency causes a dysregulation of calcium flux from the ER, which impacts on multiple collagen specific chaperones and modifying enzymatic activity, leading to a rare form of osteogenesis imperfecta (OI Type XIV). The relevance of TRIC-B on cell homeostasis and the molecular mechanism behind the disease are still unknown.</p></sec><sec><title>Results</title><p>In this study, we exploited zebrafish to elucidate the role of TRIC-B in skeletal tissue. We demonstrated, for the first time, that <italic>tmem38a</italic> and <italic>tmem38b</italic> genes encoding Tric-a and -b, respectively are expressed at early developmental stages in zebrafish, but only the latter has a maternal expression. Two zebrafish mutants for <italic>tmem38b</italic> were generated by CRISPR/Cas9, one carrying an out of frame mutation introducing a premature stop codon (<italic>tmem38b<sup>-/-</sup></italic>) and one with an in frame deletion that removes the highly conserved KEV domain (<italic>tmem38b<sup>Δ120-7/Δ120-7</sup></italic>). In both models collagen type I is under-modified and partially intracellularly retained in the endoplasmic reticulum, as described in individuals affected by OI type XIV. <italic>Tmem38b<sup>-/-</sup></italic> showed a mild skeletal phenotype at the late larval and juvenile stages of development whereas <italic>tmem38b<sup>Δ120-7/Δ120-7</sup></italic> bone outcome was limited to a reduced vertebral length at 21 dpf. A caudal fin regeneration study pointed towards impaired activity of osteoblasts and osteoclasts associated with mineralization impairment.</p></sec><sec><title>Discussion</title><p>Our data support the requirement of Tric-b during early development and for bone cell differentiation.</p></sec>