A population study of a mutation allele associated with cone–rod dystrophy in the standard wire-haired dachshund

Cone–rod dystrophy in the standard wire-haired dachshund (SWHD) is inherited as a simple autosomal recessive trait and the recently discovered mutation is widespread within the SWHD population in Norway and other Scandinavian countries. The gene frequency was estimated to be 4.8%. On the basis of the assumption that the size of the ancestral haplotype around a mutation is inversely correlated with the number of generations since the mutation arose, we have found that the mutation is of a relatively recent origin. The conserved haplotype was found to be 8 Mb in size and therefore we estimate that the mutation arose roughly eight generations (approximately 37 years) ago. This indicates that the mutation arose after breed separation.     

Dopamine D4 receptor-mediated regulation of rod opsin mRNA expression in tiger salamander

Light stimulates dopamine release in the retina and has been shown to rapidly up-regulate rod opsin mRNA. In the present study, we tested the effect of dopamine on rod opsin mRNA expression and examined the hypothesis that dopamine can mediate a light-evoked increase in opsin gene expression. Northern blots showed that a 30-min light-exposure increased rod opsin mRNA expression 27%. In situ hybridization on isolated rods showed that 500 nM dopamine and 1 microM quinpirole (dopamine D2/D3/D4 agonist) increased opsin mRNA 45% and 26%, respectively. The effect of quinpirole was selectively blocked by the D4 antagonist, L750,667 (20 microM). In very low density cultures, quinpirole increased opsin expression 46%, suggesting a direct effect on rod photoreceptors. Consistent with a dopamine D4 receptor mechanism, 1 microM H-89 (protein kinase A inhibitor) increased opsin mRNA 39%. Finally, intravitreal injection of quinpirole increased opsin mRNA 21% whereas injection of L750,667 (10 microM) blocked the light-evoked increase in opsin expression. These data show that rod opsin mRNA is up-regulated by dopamine binding a D4-like receptor on rods, possibly through inhibition of protein kinase A, and that endogenous dopamine can mediate the light-evoked increase in opsin mRNA expression.     

Transcriptional regulation of the human TATA binding protein gene

The human TATA binding protein (TBP) locus consists of a functional domain of three closely linkedhousekeeping genes (TBP, PSMB1 (proteasomal C5 subunit), and PDCD2 (programmed cell death-2)) within a 50-kb interval at chromosome position 6q27. Here we demonstrate that a genomic clone spanning the 20-kb TBP gene, with 12 kb 5' and 3' flanking sequences, was fully functional in stable, transfected L-cells harboring a single copy of this transgene, including after long-term (60 day) culture in the absence of drug selective pressure. Furthermore, we were only able to detect DNaseI hypersensitive sites at the TBP and PSMB1 promoters present within this 44-kb fragment. Our data suggest that this 44-kb genomic region possesses genetic regulatory elements that not only drive ubiquitous expression of TBP but also negate chromatin and DNA methylation induced silencing, which is normally associated with transgenes stably integrated into tissue culture cells.     

Expression of the Otx2 homeobox gene in the developing mammalian brain: embryonic and adult expression in the pineal gland

Otx2 is a vertebrate homeobox gene, which has been found to be essential for the development of rostral brain regions and appears to play a role in the development of retinal photoreceptor cells and pinealocytes. In this study, the temporal expression pattern of Otx2 was revealed in the rat brain, with special emphasis on the pineal gland throughout late embryonic and postnatal stages. Widespread high expression of Otx2 in the embryonic brain becomes progressively restricted in the adult to the pineal gland. Crx (cone-rod homeobox), a downstream target gene of Otx2, showed a pineal expression pattern similar to that of Otx2, although there was a distinct lag in time of onset. Otx2 protein was identified in pineal extracts and found to be localized in pinealocytes. Total pineal Otx2 mRNA did not show day-night variation, nor was it influenced by removal of the sympathetic input, indicating that the level of Otx2 mRNA appears to be independent of the photoneural input to the gland. Our results are consistent with the view that pineal expression of Otx2 is required for development and we hypothesize that it plays a role in the adult in controlling the expression of the cluster of genes associated with phototransduction and melatonin synthesis.     

Transcriptional regulation of the cartilage intermediate layer protein (CILP) gene

Cartilage intermediate layer protein (CILP) is an extracellular matrix protein abundant in cartilaginous tissues. CILP is implicated in common musculoskeletal disorders, including osteoarthritis and lumbar disc disease. Regulation of the CILP gene is largely unknown, however. We have found that CILP mRNA expression is induced by TGF-β1 and dependent upon signaling via TGF-β receptors. TGF-β1 induction of CILP is mediated by Smad3, which acts directly through cis-elements in the CILP promoter region. Pathways other than Smad3 also are involved in TGF-β1 induction of CILP. These observations, together with the finding that CILP protein binds and inhibits TGF-β1, suggest that CILP and TGF-β1 may form a functional feedback loop that controls chondrocyte metabolism.