Marie-Geneviève Mattei

Chromosomal mapping of A1 and A2 adenosine receptors, VIP receptor, and a new subtype of serotonin receptor.

cDNA clones encoding four new receptors of the G-protein-coupled receptor family were obtained by selective amplification and cloning from thyroid cDNA and termed RDC1, RDC4, RDC7, and RDC8. RDC7 and RDC8 have recently been identified as A1 and A2 adenosine receptors, respectively. These cDNAs were utilized for chromosomal in situ hybridization to establish the genomic location of the corresponding genes in man. The results indicate that human RDC1, RDC4, RDC7, and RDC8 are in regions 2q37, 1p34.3-1p36.3, 22q11.2-22q13.1, and 11q11-11q13, respectively.

Localization of the human c-kit protooncogene on the q11–q12 region of chromosome 4

SummaryUsing a 166-nucleotide-long DNA synthetic probe corresponding to the v-kit sequence (1458-1623), we have mapped the human c-kit gene to chromosome 4 at the q11–q12 band by in situ hybridization on chromosomes from human lymphocyte preparations.

Short communicationMapping of the human BAX gene to chromosome 19q13.3–q13.4 and isolation of a novel alternatively spliced transcript, BAXδ☆

The BAX gene is a member of the Bcl-2 gene family; it encodes a 21-kDa protein whose association with Bcl-2 is believed to play a critical role in regulating apoptosis. Through analysis of human-hamster somatic cell hybrid DNA and by in situ hybridization to metaphase chromosomes, we have determined that the human BAX gene is located in the q13.3-q13.4 region of human chromosome 19. We have also isolated a BAX cDNA clone in which that part of the mRNA encoded by exon 3 is absent. The skipping of exon 3 and the resultant splicing of exons 2 and 4 maintains the original reading frame and predicts the existence of an interstitially truncated form of the major Bax protein (Bax alpha), termed Bax delta. Unlike two previously described variant forms of Bax alpha (Bax beta and Bax tau), Bax delta retains the functionally critical C-terminal membrane anchor region as well as the Bcl-2 homology 1 and 2 (BH1 and BH2) domains.

Fertile Homozygous Transgenic Mice Expressing a Functional Truncated Herpes Simplex Thymidine Kinase ΔTK Gene

Dividing cells expressing the Herpes simplex type 1 thymidine kinase (TK) can be killed upon ganciclovir treatment. Likewise, conditional cell knock-out can be obtained in transgenic mice expressing a TK gene placed under the control of tissue-specific regulatory sequences. Such animals provide powerful experimental systems for assessing the functional role of specific cell populations through their time-controlled ablation. However, whatever the regulatory sequences used, a leaky toxic overexpression of TK in testis renders male TK-transgenic mice sterile and prevents the generation of homozygous TK-expressing animals. To solve this problem, we designed a truncated TK variant (ΔTK) not expressed in the testis. We generated transgenic mice expressing ΔTK under the control of lymphocyte-specific regulatory sequences derived from the CD4 gene. The ΔTK protein expressed in T-lymphocytes allowed the conditional ablation of activated T-cells in vitro and in vivo. Importantly, for one transgenic line we could generate fertile homozygous mice harboring a functional ΔTK transgene. ΔTK should thus dramatically facilitate the development of transgenic mice expressing a conditional suicide gene.

Localization of the thyroglobulin gene by in situ hybridization to human chromosomes.

SummaryThe human thyroglobulin gene was mapped by in situ hybridization whereby a 3H-labeled recombinant plasmid DNA containing a fragment of 2.3 kilobases of human thyroglobulin gene was hybridized to human chromosome preparations. A high proportion (25%) of hybridized metaphases exhibited silver grains at the distal portion of the long arm of chromosome 8. Analysis of the grain position at this site indicated that the chromosomal localization of the human thyroglobulin gene was 8q242-8q243.

The human calbindin D28k (CALB1) and calretinin (CALB2) genes are located at 8q21.3→q22.1 and 16q22→q23, respectively, suggesting a common duplication with the carbonic anhydrase isozyme loci

The genes encoding calbindin D28k (CALB1) and calretinin (CALB2), two closely related calcium-binding proteins, were mapped by in situ hybridization to the 8q21.3----q22.1 and 16q22----q23 regions of the human genome, respectively. These localizations match the chromosomal regions where the carbonic anhydrase isozyme gene cluster (CA1, CA2, CA3) and the related gene CA7 have been described, respectively. This suggests a common duplication o the calbindin/calretinin and the carbonic anhydrase ancestral genes.

The OLFR1 gene encoding the HGMP07E putative olfactory receptor maps to the 17p13→p12 region of the human genome and reveals an MspI restriction fragment length polymorphism

Olfactory receptors are believed to be encoded by an extremely large subfamily of G protein-coupled receptors. A human gene (OLFR1) encoding a member of this family was cloned from a genomic library by cross-hybridization with a gene fragment obtained by the polymerase chain reaction. The nucleotide sequence of a 3.4-kb EcoRI fragment was determined, and the protein sequence was deduced from the single open reading frame. The gene was assigned by in situ hybridization of metaphase chromosomes to the 17p13-->p12 region of the human genome, in proximity to the tumor-suppressor gene encoding p53. When used as a probe on Southern blots under moderately stringent conditions, it hybridizes to at least three closely related genes. A restriction fragment length polymorphism was detected after MspI digestion. Mendelian segregation of the gene was assessed in three CEPH families, and linkage analysis confirmed the localization of the locus.

The human pre-B-specific λ-like cluster is located in the 22q11.2–22q12.3 region, distal to the IgCλ locus

The chromosomal location of the lambda-like gene cluster, a gene family selectively expressed in human pre-B cells, was analyzed by in situ hybridization with a probe specific for the lambda-like genes. This cluster mapped in the q11.2-q12.3 region of chromosome 22. The use of Burkitt lymphoma and myelogenous leukemia cell lines with translocations in the 22q11 region led to a refinement in the location according to the following order: cen----BCRL2, VpreB, IgV lambda 1----BCRL4, IgV lambda----IgC lambda----BCR----BCRL3, lambda-like----tel. Unlike those of the mouse system, the pre-B-specific genes VpreB and lambda-like do not belong to the same transcriptional unit.

A novel C2H2 zinc-finger protein gene (ZNF160) maps to human chromosome 19q13.3-q13.4.

The human genome may contain up to 400 genes encoding zinc-finger (ZNF) proteins; a high proportion of those mapped have been localized to human chromosome 19. Heubner and colleagues have mapped 6 cDNAs containing a ZNF motif to 19q, and one to 19p, using somatic cell hybrids. Ten further sequences were regionally assigned by Lichter and colleagues, with a retinoic acid inducible ZNF gene being mapped to 19q13.2-q13.4. Thirty-nine cosmids identified on the basis of cross-hybridization to a ZNF {open_quotes}linker{close_quotes} sequence were mapped by FISH, 24 mapping to 19p and 15 to 19q. However, it is not known which of these sequences are transcribed or encode the cDNAs mentioned above. Forty Kruppel C{sub 2}H{sub 2}-related genes have been mapped to a cluster on 19p12-p13.1. It is interesting that none of these genes is detectable in the mouse or rat genomes, suggesting a relatively recent evolutionary origin for this cluster. 12 refs., 1 fig.

Clinical and Genetic Heterogeneity of Leber’s Congenital Amaurosis

Leber’s congenital amaurosis (LCA), originally described by Leber in 1869, is an autosomal recessively inherited congenital retinal blindness (OMIM 204000, 204001). LCA has been regarded as one of the most frequent cause of blindness in institutions for visually handicaped children,10% to 20% of the children being affected by this disease (Alstrom, 1957). LCA is clinically considered as a separate entity from retinitis pigmentosa and is characterized by its precocity and severity (Foxman, 1985). The diagnosis is usually made at birth or during the first months of life when a child presenting signs of very severely impaired vision is found to have an extinguished electro-retinogram (ERG) (Franchescetti, 1954).