The CASK/Lin-2 Drosophila homologue, Camguk, could play a role in epithelial patterning and in neuronal targeting.

Drosophila Camguk (Cmg) is a member of the CAMGUK subfamily of the MAGUK family of proteins which are localized at cell junction and other plasma membrane specialized regions, from worms to mammals. The protein structure of Cmg, as the other CAMGUK proteins, is characterized by only one PDZ domain and an additional CaM kinase domain, similar to CaMKII. While the mammalian ortholog CASKs play an important role in synaptic protein targeting and in synaptic plasticity, the Drosophila Cmg role is unknown. To study its potential role, we reported a detailed analysis of mRNA distribution of the Drosophila cmg gene at cellular and developmental level, during embryonic, larval, pupal and adult stages. The transient cmg transcription in midgut and Malpighian tubules may suggest a potential function in cell junction formation and in epithelial tissue patterning. Interestingly, cmg transcription increases substantially during embryonic neuroblast proliferation, becoming predominant in the developing central nervous system (CNS) during embryonic and postembryonic development stages and in the mature brain. In addition, a high transcriptional level was detected in the eye imaginal discs and in the adult retina, demonstrating a specific and continuous expression of cmg in neuroblasts and photoreceptor neurons, from the onset of cytodifferentiation. Our findings suggest that Cmg could play a potential role in transmembrane protein targeting, particularly in synapses. These observations suggest the existence of a common highly conserved mechanism involved in forming and maintaining proper synaptic protein targeting, which are fundamental features of synaptic plasticity, learning and memory. Through its function, the CaM kinase domain-containing Cmg may be involved in signal transduction cascade. Its potential relation to Calmodulin and CaMKII is discussed.

Regional and cellular specificity of the expression of TPRD, the tetratricopeptide Down syndrome gene, during human embryonic development.

The TPRD gene (tetratricopeptide (TPR) containing Down syndrome gene) is one of the candidate genes in the Down syndrome chromosomal region-1. Duplication of this gene may be the cause of major phenotypic features of Down syndrome. Here we show that the TPRD expression is developmentally regulated during human embryogenesis. At the earliest stages of development (Carnegie 8-12) TPRD expression is ubiquitous. At later developmental stages (Carnegie stages 14, 16 and 18), it becomes restricted to the nervous system, as is the case for the mtprd gene during mouse development. We extended our analysis of TPRD expression during fetal development of the human nervous system (13, 22 and 24 weeks). A new oblique illumination technique was used to compare signal intensity and cell density. Some regions of the nervous system such as the external cortical layers of the brain, and the inner neuroblastic layer of the eye, strongly express the TPRD gene.

Developmentally regulated expression of mtprd, the murine ortholog of tprd, a gene from the Down syndrome chromosomal region 1.

The gene tprd, which contains three tetratricopeptide domains, has been recently localized in the Down syndrome (DS) chromosomal region 1. We have cloned a cDNA encoding part of the murine ortholog of tprd and used it to characterize the expression pattern of this gene during development and at the adult stage. At E8.5 the expression is uniform. In the later stages of embryogenesis, although expression remains ubiquitous, a pattern of tissues with particularly high expression develops: the strong expression is restricted to non proliferating zones of the nervous system such as the external layer of the cortex, the spinal cord, the cranial and root ganglia and the nerves. In the brain of adult mouse the strongest signals are observed in layers II-III and V-VI of the cortex, in the hippocampus and in the cerebellum, which correspond to the abnormal brain regions seen in DS patients.