RESUMO
CD28 is a cell surface molecule present on most peripheral T cells which has been implied in the amplification of the T-cell response in vitro. Using in situ hybridization on human prometaphase cells, we have found that the human CD28 gene maps to chromosome 2 at bands q33-q34, as shown previously for the CTLA-4 gene. CD28 and CTLA-4 are both members of the Ig superfamily, where they define a subgroup of membrane-bound single V domains. Their chromosomal proximity and their close structural relationship suggest that these two genes could be the result of the duplication of a common evolutionary precursor and may share some functional properties.
Assuntos
Antígenos CD/genética , Antígenos de Diferenciação de Linfócitos T/genética , Cromossomos Humanos Par 2/análise , Família Multigênica , Autorradiografia , Antígenos CD28 , Mapeamento Cromossômico , Humanos , Masculino , Hibridização de Ácido NucleicoAssuntos
Fosfatase Alcalina/genética , Mapeamento Cromossômico , Isoenzimas/genética , Placenta/enzimologia , Regiões Promotoras Genéticas , Sequência de Bases , Cromossomos Humanos Par 2/análise , Clonagem Molecular , Cosmídeos , Proteínas Ligadas por GPI , Genes , Humanos , Dados de Sequência Molecular , Polimorfismo de Fragmento de Restrição , Homologia de Sequência do Ácido NucleicoRESUMO
The nicotinic acetylcholine receptor of skeletal muscle (CHRN in man, Acr in mouse) is a transmembrane protein composed of four different subunits (alpha, beta, gamma, and delta) assembled into the pentamer alpha 2 beta gamma delta. These subunits are encoded by separate genes which derive from a common ancestral gene by duplication. We have used a murine full-length 1,900-bp-long cDNA encoding the gamma subunit subcloned into M 13 (clone gamma 18) to prepare single-stranded probes for hybridization to EcoRI-digested DNA from a panel of human x rodent somatic cell hybrids. Using conditions of low stringency to favor cross-species hybridization, and prehybridization with rodent DNA to prevent rodent background, we detected a single major human band of 30-40 kb. The pattern of segregation of this 30-40 kb band correlated with the segregation of human chromosome 2 within the panel and the presence of a chromosomal translocation in the distal part of the long arm of this t(X;2)(p22;q32.1) chromosome allowing the localization of the gamma subunit gene (CHRNG) to 2q32----qter. The human genes encoding the gamma and delta subunits have been shown to be contained in an EcoRI restriction fragment of approximately 20 kb (Shibahara et al., 1985). Consequently, this study also maps the delta subunit gene (CHRND) to human chromosome 2q32.1----qter. In the mouse, the Acrd and Acrg genes have been shown to be linked to Idh-1, Mylf (IDH1 and MYL1 in humans, respectively) and to the gene encoding villin on chromosome 1. Interestingly, we have recently localized the human MYL1 gene to the same chromosomal fragment of human chromosome 2. These results clearly demonstrate a region of chromosomal homoeology between mouse chromosome 1 and human chromosome 2.
Assuntos
Mapeamento Cromossômico , Cromossomos Humanos Par 2/ultraestrutura , Receptores Colinérgicos/genética , Animais , Cromossomos Humanos Par 2/análise , Cricetinae , DNA/análise , DNA/genética , Sondas de DNA , Marcadores Genéticos/análise , Humanos , Células Híbridas/ultraestrutura , Camundongos , Hibridização de Ácido Nucleico , Receptores Nicotínicos/genéticaRESUMO
The practical applications and improvements to a fast scanning microscope photometer system are described. The production of a density profile is demonstrated which, when taken in conjunction with the chromosome scan, allows more information to be extracted from the data than was previously possible. This enables a more accurate correlation to be made between phenotype and karyotype. The system is demonstrated on preparations of known cytogenetically abnormal individuals, showing the range of problems which can be tackled.
