Expression of FET-1 related transcripts during chicken embryogenesis suggests a role in muscle development

The genetic basis of somatic cell identity in avian sex determination is still unknown. FET1, an endogenous retrovirus, has previously been demonstrated to be expressed during gonad development. Here, we report expression of FET1 related transcripts in non-gonadal tissue during chicken development. Both the forward and reverse FET1 related transcripts were seen in various developing muscle tissues. Both the "full-length" and partial FET1 transcripts were expressed; the latter however showed a more ubiquitous expression pattern. Female-specific gonadal expression of both sense and antisense transcripts was also confirmed. An anti-FET1 antibody, however, failed to distinguish between the predicted FET1 protein and other endogenous retroviral proteins expressed at E6.5. Our data suggest a possible role for FET1 related transcripts in sex-specific differences in muscle size and growth rate in the chickens.