title: CLPH, a novel casein kinase 2-phosphorylated disordered protein, is specifically associated with postmeiotic germ cells in rat spermatogenesis.
abstract: In a recent proteomic study of rat spermatogenesis, we identified CLPH (for Casein-Like PHosphoprotein), a new testis-specific protein expressed exclusively in postmeiotic germ cells. In situ hybridization showed that the CLPH transcript was mainly present in round spermatids, whereas the protein was specifically detected by immunohistochemistry in elongated spermatids and in residual bodies. Electron microscopy showed the protein to be mostly cytoplasmic, but also frequently associated with the mitochondrial inner membrane during the last steps of spermatid differentiation. The Clph gene was found to be present solely in mammalian genomes, in a chromosomal region syntenic to the mammalian cluster of secretory calcium-binding phosphoprotein (SCPP) genes. CLPH has several distinctive properties in common with SCPPs: calcium overlay experiments showed that CLPH was a calcium-binding protein, whereas trypsin digestion assay, circular dichroism and fluorescence experiments demonstrated its intrinsically disordered structure. We also showed that CLPH was phosphorylated in vitro and in vivo by casein kinase 2, an enzyme critical for spermatid elongation. Given the specific and strong production of CLPH during rat spermiogenesis, together with the particular biochemical properties of this protein, we suggest that CLPH is involved in the extremely complex structural rearrangements occurring in haploid germ cells during spermiogenesis.
authors.affiliation: Inserm, U625, Rennes, Universite Rennes I, Campus de Beaulieu, IFR-140, GERHM, Rennes, F-35042, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Calvel
authors.forename: Christine
authors.initials: C
authors.lastname: Kervarrec
authors.forename: Régis
authors.initials: R
authors.lastname: Lavigne
authors.forename: Virginie
authors.initials: V
authors.lastname: Vallet-Erdtmann
authors.forename: Myriam
authors.initials: M
authors.lastname: Guerrois
authors.forename: Antoine D
authors.initials: AD
authors.lastname: Rolland
authors.forename: Frédéric
authors.initials: F
authors.lastname: Chalmel
authors.forename: Bernard
authors.initials: B
authors.lastname: Jégou
authors.forename: Charles
authors.initials: C
authors.lastname: Pineau
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II / Q000378:metabolism; D002364:Caseins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003198:Computer Simulation; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D017403:In Situ Hybridization; D008297:Male; D013058:Mass Spectrometry; D008540:Meiosis; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017510:Protein Folding; D040901:Proteomics; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013087:Spermatids / Q000378:metabolism*; D013091:Spermatogenesis; D013737:Testis / Q000166:cytology / Q000378:metabolism
chemical_list: C543433:Cabs1 protein, rat; D002364:Caseins; D047390:Casein Kinase II