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Germ cells play a unique role in heredity and evolution as carriers of genetic information across generations, but the study of the early stage of germ cell specification is still an overlooked issue.In this study, we documented the earliest stages of germ cell specification in Ruditapes philippinarum (the Manila clam), describing both the mechanism and timing. Initially, we focused our investigation on OSKAR, the necessary and sufficient factor involved in the earliest stage of Drosophila germline specification. On the basis of bioinformatic analyses we identified a Tudor domain-containing protein 7 (TDRD7) as the possible best candidate acting in the corresponding stage of germline specification in R. philippinarum. This hypothesis is supported by domain similarities between OSKAR and TDRD7, as well as in situ localization of the latter in putative germ cells in their earliest stage of differentiation from germline stem cells.In this light, germline specification appears to show evolutionarily conserved features, while maintaining some kind of plasticity, thus allowing differences among different taxa. Although OSKAR orthologues are not known outside insects, a corresponding role in other animals has to be carried out, possibly by different proteins with similar functions. We propose TDRD7 as a germline factor acting at early stages of germline specification in R. philippinarum, thus a good candidate as OSKAR functional-homolog.

The olfactory epithelium of fish includes three main types of olfactory sensory neurons (OSNs). Whereas ciliated (cOSNs) and microvillous olfactory sensory neurons (mOSNs) are common to all vertebrates, a third, smaller group, the crypt cells, is exclusive for fish. Dissolved pollutants reach OSNs, thus resulting in impairment of the olfactory function with possible neurobehavioral damages, and nickel represents a diffuse olfactory toxicant. We studied the effects of three sublethal Ni2+ concentrations on the different OSN populations of zebrafish that is a widely used biological model. We applied image analysis with cell count and quantification of histochemically-detected markers of the different types of OSNs. The present study shows clear evidence of a differential responses of OSN populations to treatments. Densitometric values for Gα olf, a marker of cOSNs, decreased compared to control and showed a concentration-dependent effect in the ventral half of the olfactory rosette. The densitometric analysis of TRPC2, a marker of mOSNs, revealed a statistically significant reduction compared to control, smaller than the decrease for Gα olf and without concentration-dependent effects. After exposure, olfactory epithelium stained with anti-calretinin, a marker of c- and mOSNs, revealed a decrease in thickness while the sensory area appeared unchanged. The thickness reduction together with increased densitometric values for HuC/D, a marker of mature and immature neurons, suggests that the decrements in Gα olf and TRPC2 immunostaining may depend on cell death. However, reductions in the number of apical processes and of antigen expression could be a further explanation. We hypothesize that cOSNs are more sensitive than mOSNs to Ni2+ exposure. Difference between subpopulations of OSNs or differences in water flux throughout the olfactory cavity could account for the greater susceptibility of the OSNs located in the ventral half of the olfactory rosette. Cell count of anti-TrkA immunopositive cells reveals that Ni2+ exposure does not affect crypt cells. The results of this immunohistochemical study are not in line with those obtained by electro-olfactogram.

Hearing loss, or deafness, affects 360 million people worldwide of which about 32 million are children. Deafness is irreversible when it involves sensory hair cell death because the regenerative ability of these cells is lost in mammals after embryo development. The therapeutic strategies for deafness include hearing aids and/or implantable devices. However, not all patients are eligible or truly benefit from these medical devices. Regenerative medicine based on stem cell application could play a role in both improvement of extant medical devices and in vivo recovery of auditory function by regeneration of inner ear cells and neurons. A review of recent literature on the subject indicates that two promising approaches to renewal and differentiation of cochlear tissues are transplantation of stem cells and in situ administration of growth factors. Rather than directly regenerating dead cells, these procedures apparently induce, through various pathways, differentiation of resident cochlear cells. More studies on the possible adverse effects of transplanted cells and the recovery of tonotopic sensorineural activity or required. To date, no reliable clinical results have been obtained in the field of cochlear regeneration.

Background Cutaneous squamous cell carcinoma (cSCC) is an uncommon disease affecting koi carp (Cyprinus carpio). Cutaneous papilloma (carp pox) is a benign epidermal proliferation reported in koi and has been shown to be caused by Cyprinid Herpesvirus 1 (CyHV1). Hypothesis/Objectives Histological, ultrastructural and molecular investigations were carried out aiming to investigate the aetiology of cSCC within archived tissue samples. Animals Surgical samples of masses located on the integument, fins and lips of 13 koi carp belonging to different private owners were included in this retrospective study. Methods CyHV1 DNA and RNA presence were investigated in five cSCC formalin-fixed paraffin-embedded tissue samples to recognize CyHV1 presence and its replication activity. Results All cases were histologically diagnosed as cSCC. The ultrastructural observations confirmed the squamous differentiation of neoplastic epithelial cells, which showed abundant tonofilament bundles and desmosomes. Although no virus particles were revealed ultrastructurally, the molecular investigation detected viral DNA in five epidemiologically unrelated cSCC. Viral transcript analysis revealed no evidence for viral replication in the tested cSCC, which could be consistent with latent infection. Conclusions and clinical importance These findings illustrate the frequent association of carp cSCC with CyHV1, although a direct cause–effect relationship cannot be established at this time. Therefore, surveillance programmes should take into account the suspected viral origin of cSCC to better inform prevention and control of CyHV1 in the future.