SANS (USH1G) expression in developing and mature mammalian retina.

The human Usher syndrome (USH) is the most common form of combined deaf-blindness. Usher type I (USH1), the most severe form, is characterized by profound congenital deafness, constant vestibular dysfunction and prepubertal-onset of retinitis pigmentosa. Five corresponding genes of the six USH1 genes have been cloned so far. The USH1G gene encodes the SANS (scaffold protein containing ankyrin repeats and SAM domain) protein which consists of protein motifs known to mediate protein-protein interactions. Recent studies indicated SANS function as a scaffold protein in the protein interactome related to USH. Here, we generated specific antibodies for SANS protein expression analyses. Our study revealed SANS protein expression in NIH3T3 fibroblasts, murine tissues containing ciliated cells and in mature and developing mammalian retinas. In mature retinas, SANS was localized in inner and outer plexiform retinal layers, and in the photoreceptor cell layer. Subcellular fractionations, tangential cryosections and immunocytochemistry revealed SANS in synaptic terminals, cell-cell adhesions of the outer limiting membrane and ciliary apparati of photoreceptor cells. Analyses of postnatal developmental stages of murine retinas demonstrated SANS localization in differentiating ciliary apparati and in fully developed cilia, synapses, and cell-cell adhesions of photoreceptor cells. Present data provide evidence that SANS functions as a scaffold protein in USH protein networks during ciliogenesis, at the mature ciliary apparatus, the ribbon synapse and the cell-cell adhesion of mammalian photoreceptor cells. Defects of SANS may cause dysfunction of the entire network leading to retinal degeneration, the ocular symptom characteristic for USH patients.

Vezatin, a ubiquitous protein of adherens cell-cell junctions, is exclusively expressed in germ cells in mouse testis.

In the male reproductive organs of mammals, the formation of spermatozoa takes place during two successive phases: differentiation (in the testis) and maturation (in the epididymis). The first phase, spermiogenesis, relies on a unique adherens junction, the apical ectoplasmic specialization linking the epithelial Sertoli cells to immature differentiating spermatids. Vezatin is a transmembrane protein associated with adherens junctions and the actin cytoskeleton in most epithelial cells. We report here the expression profile of vezatin during spermatogenesis. Vezatin is exclusively expressed in haploid germ cells. Immunocytochemical and ultrastructural analyses showed that vezatin intimately coincides, temporally and spatially, with acrosome formation. While vezatin is a transmembrane protein associated with adherens junctions in many epithelial cells, it is not seen at the ectoplasmic specializations, neither at the basal nor at the apical sites, in the seminiferous epithelium. In particular, vezatin does not colocalize with espin and myosin VIIa, two molecular markers of the ectoplasmic specialization. In differentiating spermatids, ultrastructural data indicate that vezatin localizes in the acrosome. In epididymal sperm, vezatin localizes also to the outer acrosomal membrane. Considering its developmental and molecular characteristics, vezatin may be involved in the assembly/stability of this spermatic membrane.

Vitellogenin from female and estradiol-stimulated male river lampreys (Lampetra fluviatilis L.).

The influence of estradiol-17beta (E(2)) on vitellogenesis is well documented for a number of oviparous craniates. We have examined the role that estradiol-17beta plays in the induction and regulation of vitellogenin synthesis in the maturing European river lamprey, Lampetra fluviatilis. In both females and males the estradiol-17beta concentrations in the plasma reached comparable maximum values in March, only a few weeks before spawning. Throughout the spawning run, the vitellogenin titer in the blood of females remains rather constant while the ovary volume increases. In contrast, we never found circulating VTG in untreated male lampreys. The synthesis and secretion of the yolk precursor molecule can be induced in males, however, by high doses of estradiol injected into the coelom. Lamprey vitellogenin was isolated from the blood of maturing females as well as from hormone-stimulated males and identified by its immunological and electrophoretic properties. In the blood plasma of both maturing female and estradiol-treated male lampreys it always appears simultaneously in two different molecular forms: a vitellogenin monomer with an apparent molecular weight of 310-330kDa and a dimer. After SDS treatment, vitellogenin is represented as a 212-kDa polypeptide.