C455R notch3 mutation in a Colombian CADASIL kindred with early onset of stroke.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is caused by mutations in the notch3 epidermal growth factor-like repeats. A Colombian kindred carries a novel C455R mutation located in the predicted ligand-binding domain. Stroke occurred in the patients at an unusually early age (median age: 31 years) in comparison to the more frequent onset in the fourth decade of life in other CADASIL populations, including a second Colombian kindred with an R1031C mutation.

Coactivator and corepressor gene expression in rat cerebellum during postnatal development and the effect of altered thyroid status.

Thyroid hormone (TH) plays an important role in the postnatal development of the rodent cerebellum, particularly within the first 2 weeks of postnatal life. This action is exerted through the regulation of specific genes during development and is mediated by coactivator and corepressor proteins that determine transcriptional repression or activation, respectively. Thus, we hypothesized that the effect of TH on rodent cerebellar development could be influenced by the relative amounts of coactivator and corepressor proteins in vivo. These ratios might be modulated in an age-specific manner and/or by hormones to generate the "critical period" of TH action. To examine this hypothesis, we cloned rat complementary DNA fragments corresponding to coactivators (SRC1, TIF2 and TRAM1) and corepressors (N-CoR and SMRT), and studied the ontogenic changes in their corresponding messenger RNAs in rat cerebellum of normal and hypothyroid rats during postnatal development, using a RNase protection assay. We found an increased expression of SRC1 and TIF2, as well as of N-CoR, during rat cerebellar development but no change in the expression of SMRT and TRAM1 genes. However, thyroid hormone status did not affect the expression of coactivator and corepressor genes in the cerebellum. These results indicate that coactivator and corepressor messenger RNAs exhibit differential expression through cerebellar development but are not regulated by TH during this period.

The human RC3 gene homolog, NRGN contains a thyroid hormone-responsive element located in the first intron.

NRGN is the human homolog of the neuron-specific rat RC3/neurogranin gene. This gene encodes a postsynaptic 78-amino acid protein kinase substrate that binds calmodulin in the absence of calcium, and that has been implicated in dendritic spine formation and synaptic plasticity. In the rat brain RC3 is under thyroid hormone control in specific neuronal subsets in both developing and adult animals. To evaluate whether the human gene is also a target of thyroid hormone we have searched for T3-responsive elements in NRGN cloned genomic fragments spanning the whole gene. Labeled DNA fragments were incubated with T3 receptors (T3R) and 9-cis-retinoic acid receptors and immunoprecipitated using an anti T3R antibody. A receptor-binding site was localized in the first intron, 3000 bp downstream from the origin of transcription. Footprinting analysis revealed the sequence GGATTAAATGAGGTAA, closely related to the consensus T3-responsive element of the direct repeat (DR4) type. This sequence binds the T3R-9-cis-retinoic acid receptors heterodimers, but not T3R monomers or homodimers, and is able to confer regulation by T3R and T3 when fused upstream of the NRGN or thymidine kinase promoters. The data reported in this work suggest that NRGN is a direct target of thyroid hormone in human brain, and that control of expression of this gene could underlay many of the consequences ofhypothyroidism on mental states during development as well as in adult subjects.

Identification of a cis-acting element that interferes with thyroid hormone induction of the neurogranin (NRGN) gene.

The neuron-specific RC3/neurogranin gene is regulated by thyroid hormone at the transcriptional level in brain and in cultured neuronal cells. Regulation in vivo displays exquisite regional selectivity which is not due to differential distribution of thyroid receptors and is most probably related to region-specific trans-acting elements. We have previously identified an intronic thyroid hormone responsive element in the human RC3 gene homolog, NRGN. In a search for cis-acting elements that might contribute to the specificity of thyroid regulation, we have identified a novel sequence, TTCCAAAATGG, which binds to a developmentally regulated protein, and interferes with T3 transactivation.

Structure, organization, and chromosomal mapping of the human neurogranin gene (NRGN).

In this report the identification, structure, and chromosomal localization of the human neurogranin gene (NRGN) are described. NRGN is the human homolog of the rat Ng/RC3 gene, which encodes a brain-specific protein expressed in telencephalic neurons. The human NRGN gene spans approximately 12 kb and contains four exons and three introns. All splice acceptor and donor sites conform to the canonical AG/GT rule. Human neurogranin sequence predicts a 78-amino-acid protein with 5 amino acids encoded by exon 1 and the remaining 73 amino acids encoded by exon 2. The third and fourth exons contain untranslated sequences. The overall degree of homology between the human and the rat coding sequences is 90% for the nucleic acid sequence, with 96% identity and 97.5% similarity at the protein level. The NRGN gene is expressed exclusively in brain as a single 1.3-kb mature mRNA. The promoter lacks both TATA and CAAT boxes, but shows a consensus sequence for an initiator element located 234 bases upstream from the AUG initiation codon. The 5'-flanking region contains multiple putative binding sites for transcription factors such as Sp1, GCF, AP2, and PEA3. Analysis of a panel of radiation hybrids has led to localization of the NRGN gene in YAC 763A2 (CEPH), previously mapped at 11q24. This locus is contained in a region of conserved synteny with mouse chromosome 9.