人类基因组17q11—q12：癌基因与抗癌基因富集区

由于人基因组１７ｑ１１－ｑ１２含有许多与癌发生有关的基因,因此成了人们研究的热点。本仅就该区域的基因克隆、基因组制图以及这些基因与癌发生的关系作一详细介绍。     

Characterisation of interstitial duplications and triplications of chromosome 15q11–q13

Chromosome 15 is frequently involved in the formation of structural rearrangements. We report the molecular characterisation of 16 independent interstitial duplications, including those of one individual who carried a duplication on both of her chromosomes 15, and three interstitial triplications of the Prader-Willi/Angelman syndrome critical region (PWACR). In all probands except one, the rearrangement was maternal in origin. In one family, the duplication was paternal in origin, yet appeared to segregate in a sibship of three with an abnormal phenotype that included developmental delay and a behavioural disorder. Ten duplications were familial, five de novo and one unknown. All 16 duplications, including two not visible by routine G-banding, were of an almost uniform size and shared the common deletion breakpoints of Prader-Willi syndrome and Angelman syndrome. Like deletions, the formation of duplications can occur in both male and female meiosis and involve both inter- and intrachromosomal events. This implies that at least some deletions and duplications are the reciprocal products of each other. We observed no instances of meiotic instability in the transmission of a duplication, although recombination within the PWACR occurred in two members of the same family between the normal and the duplicated chromosome 15 homologues. All three triplications arose de novo and included alleles from both maternal chromosomes 15. Triplication breakpoints were more variable and extended distally beyond the PWACR. The molecular characteristics of duplications and triplications suggest that they are formed by different mechanisms.     

A boy with 47,X,del(X)(p11→q13::q21→q24),del(Y)(q11)

Summary A patient is described carrying a duplication 4p12pter due to a paternal translocation: 46,XY,t(4;16) (p12;p13). Involvement of chromosome No. 16 and the heterogeneity of the clinical picture in cases with dup (4p) are discussed.Postdoctoral fellow of the Deutsche Forschungsgemeinschaft.     

Autosomal recessive nonsyndromic deafness locus DFNB63 at chromosome 11q13.2–q13.3

A genome wide linkage analysis of nonsyndromic deafness segregating in a consanguineous Pakistani family (PKDF537) was used to identify DFNB63, a new locus for congenital profound sensorineural hearing loss. A maximum two-point lod score of 6.98 at θ = 0 was obtained for marker D11S1337 (68.55 cM). Genotyping of 550 families revealed three additional families (PKDF295, PKDF702 and PKDF817) segregating hearing loss linked to chromosome 11q13.2-q13.3. Meiotic recombination events in these four families define a critical interval of 4.81 cM bounded by markers D11S4113 (68.01 cM) and D11S4162 (72.82 cM), and SHANK2, FGF-3, TPCN2 and CTTN are among the candidate genes in this interval. Positional identification of this deafness gene should reveal a protein necessary for normal development and/or function of the auditory system.     

Localization of the human progesterone receptor gene to chromosome 11q22–q23

Summary The human progesterone receptor gene was mapped by in situ hybridization using two cDNA probes corresponding to the 5′ and 3′ part of the coding sequence. This gene was localized to 11q22-q23.     

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

Summary Using 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.     

New gene in the homologous human 11q13–q14 and mouse 7F chromosomal regions

Alterations in the chromosomal region 11q13–11q14 are involved in several pathologies in which most of the key genes remain to be identified. In an effort to isolate as many candidates as possible, we are cloning genes from this region. We report here the mapping for a new sequence from 11q13.5–11q14. This sequence, designated D11S833E, putatively encodes a new gene, provisionally named GARP. We cloned its homologous sequence in the mouse and located it on Chromosome (Chr) 7, region F. The human and mouse genes belong to a conserved group of synteny. This, together with the similar conservation of the FGF and TYR genes, indicates that the human 11q13–q14 and mouse 7E-7F regions share homology.     

11q;22q易位的细胞遗传学亚型——附三例高分辨显带分析

11号与22号染色体长臂之间的易位t(11q;22q)是一种比较常见的染色体异常。在不平衡易位时,它导致22号长臂的部分三体性,但患者的临床表现和文献中报告的易位断点的位置均很多样。本文对来自三个家系的3名易位携带者的外周血培养细胞染色休进行了常规和高分辨显带分析,结果发现3名携带者易位染色体的构成均为t(11q25;22ql3.1)。因此,在复习和汇总文献资料的基础上,提出此种易位目前至少可区别11q23;22qll与llq25,;22ql3两种主要细胞遗传学亚型。     

一家系三例rcp(5; 11)(q35；q13）核型报告

我室在1983年和1986年两次对一家系成员作染色体检查和家系调查，发现7人中有3例rcp (5;11)'(q35; q13）平衡易位患者。查阅文献［1,4,6,9],国内外尚无报道。     

22q11微缺失与先天性心脏病的关系的研究

应用染色体荧光原位杂交（FISH）技术,对25例不同表型的先天性心脏病患者外周血标本进行22q11微缺失的检测,以探讨先天性心脏病与22q11微缺失的关系。受检的23例单纯性先天性心脏病患者,无22q11缺失者为19例,发生缺失者为4例;2例法鲁氏四联症伴心外多发畸形患者,有22q11缺失。上述结果表明,先天性心脏病与22q11微缺失有关。     

Assignment of the apolipoprotein A-I gene to 11q23 based on RFLP in a case with a partial deletion of chromosome 11, del(11)(q23.3→qter)

Summary The XmnI genotype at the apolipoprotein A-I locus was heterozygous in a boy with partial deletion of the long arm of chromosome 11, del(11)(q23.3qter). The apolipoprotein A-I gene, previously assigned to chromosome region 11q23q24, has been more specifically localized to 11q23 by excluding the region 11q24qter.     

Congenital heart defects and 22q11 deletions: which genes count?

Hemizygous deletions on the long arm of chromosome 22 (del22q11) are a relatively common cause of congenital heart disease. For some specific heart defects such as interrupted aortic arch type B and tetralogy of Fallot with absent pulmonary valve, del22q11 is probably the most frequent genetic cause. Although extensive gene searches have been successful in discovering many novel genes in the deleted segment, standard positional cloning has so far failed to demonstrate a role for any of these genes in the disease. We show how the use of experimental animal models is beginning to provide an insight into the developmental role of some of these genes, while novel genome manipulation technologies promise to dissect the genetic aspects of this complex syndrome.     

Transposition of 9q34 and 22 (q11→qter) regions has a specific role in chronic myelocytic leukemia

Summary Six cases are reported of variant Ph translocations found among 240 patients with Ph-positive CML. Five cases had a three-chromosome rearrangement involving, in addition to chromosomes 9 and 22, chromosomes 7, 4, 2(two), and 3 respectively, and one case had a two-chromosome rearrangement 22/5. A review of the literature revealed that three- and two-chromosome variant Ph translocations are observed with equal frequency. It is postulated that all variant translocations are indeed three-chromosome rearrangements, that the specific event for the formation of the Ph chromosome is the reciprocal translocation 9/22, and that the transposition of regions 9q34 and 22 (q11qter), plays a major role in the development of CML.     

Human NK-2 receptor gene maps to chromosome region 10q11–21

Summary The human NK-2 receptor gene has been mapped to chromosome 10 using the polymerase chain reaction to amplify specifically the human NK-2 receptor sequence in hamster/human hybrid DNA and also in mouse/human monochromosome hybrids. The assignment to chromosome 10 was confirmed by in situ hybridisation to human metaphase chromosomes, giving a regional localisation of 10q11–21.     

Comparative analysis of vertebrate EIF2AK2 (PKR) genes and assignment of the equine gene to ECA15q24–q25 and the bovine gene to BTA11q12–q15

The structures of the canine, rabbit, bovine and equine EIF2AK2 genes were determined. Each of these genes has a 5'' non-coding exon as well as 15 coding exons. All of the canine, bovine and equine EIF2AK2 introns have consensus donor and acceptor splice sites. In the equine EIF2AK2 gene, a unique single nucleotide polymorphism that encoded a Tyr329Cys substitution was detected. Regulatory elements predicted in the promoter region were conserved in ungulates, primates, rodents, Afrotheria (elephant) and Insectifora (shrew). Western clawed frog and fugu EIF2AK2 gene sequences were detected in the USCS Genome Browser and compared to those of other vertebrate EIF2AK2 genes. A comparison of EIF2AK2 protein domains in vertebrates indicates that the kinase catalytic domains were evolutionarily more conserved than the nucleic acid-binding motifs. Nucleotide substitution rates were uniform among the vertebrate sequences with the exception of the zebrafish and goldfish EIF2AK2 genes, which showed substitution rates about 20% higher than those of other vertebrates. FISH was used to physically assign the horse and cattle genes to chromosome locations, ECA15q24–q25 and BTA11q12–15, respectively. Comparative mapping data confirmed conservation of synteny between ungulates, humans and rodents.     

A physical map of large segments of pig Chromosome 7q11–q14: comparative analysis with human Chromosome 6p21

The aim of this study was to establish a porcine physical map along the chromosome SSC7q by construction of BAC contigs between microsatellites Sw1409 and S0102. The SLA class II contig, located on SSC7q, was lengthened. Four major BAC contigs and 10 short contigs span a region equivalent to 800 cR measured by IMpRH7000 mapping. The BAC contigs were initiated by PCR screening with primers derived from human orthologous segments, extended by chromosome walking, and controlled and oriented by RH mapping with the two available panels, IMpRH7000Rad and IMNpRH12000Rad. The location of 43 genes was revealed by sequenced segments, either from BAC ends or PCR products from BAC clones. The 220 BAC end sequences (BES) were also used to analyze the different marks of evolution. Comparative mapping analysis between pigs and humans demonstrated that the gene organization on HSA6p21 and on SSC7p11 and q11-q14 segments was conserved during evolution, with the exception of long fragments of HSA6p12 which shuffled and spliced the SLA extended class II region. Additional punctual variations (unique gene insertion/deletion) were observed, even within conserved segments, revealing the evolutionary complexity of this region. In addition, 18 new polymorphic microsatellites have been selected in order to cover the entire SSC7p11-q14 region.     

UV light activates a Gαq/11-coupled phototransduction pathway in human melanocytes

While short exposure to solar ultraviolet radiation (UVR) can elicit increased skin pigmentation, a protective response mediated by epidermal melanocytes, chronic exposure can lead to skin cancer and photoaging. However, the molecular mechanisms that allow human skin to detect and respond to UVR remain incompletely understood. UVR stimulates a retinal-dependent signaling cascade in human melanocytes that requires GTP hydrolysis and phospholipase C β (PLCβ) activity. This pathway involves the activation of transient receptor potential A1 (TRPA1) ion channels, an increase in intracellular Ca²⁺, and an increase in cellular melanin content. Here, we investigated the identity of the G protein and downstream elements of the signaling cascade and found that UVR phototransduction is Gα_q/11 dependent. Activation of Gα_q/11/PLCβ signaling leads to hydrolysis of phosphatidylinositol (4,5)-bisphosphate (PIP₂) to generate diacylglycerol (DAG) and inositol 1, 4, 5-trisphosphate (IP₃). We found that PIP₂ regulated TRPA1-mediated photocurrents, and IP₃ stimulated intracellular Ca²⁺ release. The UVR-elicited Ca²⁺ response appears to involve both IP₃-mediated release from intracellular stores and Ca²⁺ influx through TRPA1 channels, showing the fast rising phase of the former and the slow decay of the latter. We propose that melanocytes use a UVR phototransduction mechanism that involves the activation of a Gα_q/11-dependent phosphoinositide cascade, and resembles light phototransduction cascades of the eye.     

The role of Gαq/Gα11 signaling in intestinal epithelial cells

Intestinal homeostasis and the coordinated actions of digestion, absorption and excretion are tightly regulated by a number of gastrointestinal hormones. Most of them exert their actions through G-protein-coupled receptors. Recently, we showed that the absence of Gα_q/Gα₁₁ signaling impaired the maturation of Paneth cells, induced their differentiation toward goblet cells, and affected the regeneration of the colonic mucosa in an experimental model of colitis. Although an immunohistochemical study showed that Gα_q/Gα₁₁ were highly expressed in enterocytes, it seemed that enterocytes were not affected in Int-G_q/G₁₁ double knock-out intestine. Thus, we used an intestinal epithelial cell line to examine the role of signaling through Gα_q/Gα₁₁ in enterocytes and manipulated the expression level of Gα_q and/or Gα₁₁. The proliferation was inhibited in IEC-6 cells that overexpressed Gα_q/Gα₁₁ and enhanced in IEC-6 cells in which Gα_q/Gα₁₁ was downregulated. The expression of T-cell factor 1 was increased according to the overexpression of Gα_q/Gα₁₁. The expression of Notch1 intracellular cytoplasmic domain was decreased by the overexpression of Gα_q/Gα₁₁ and increased by the downregulation of Gα_q/Gα₁₁. The relative mRNA expression of Muc2, a goblet cell marker, was elevated in a Gα_q/Gα₁₁ knock-down experiment. Our findings suggest that Gα_q/Gα₁₁-mediated signaling inhibits proliferation and may support a physiological function, such as absorption or secretion, in terminally differentiated enterocytes.     

VEGF: a modifier of the del22q11 (DiGeorge) syndrome?

Hemizygous deletion of chromosome 22q11 (del22q11) causes thymic, parathyroid, craniofacial and life-threatening cardiovascular birth defects in 1 in 4,000 infants. The del22q11 syndrome is likely caused by haploinsufficiency of TBX1, but its variable expressivity indicates the involvement of additional modifiers. Here, we report that absence of the Vegf164 isoform caused birth defects in mice, reminiscent of those found in del22q11 patients. The close correlation of birth and vascular defects indicated that vascular dysgenesis may pathogenetically contribute to the birth defects. Vegf interacted with Tbx1, as Tbx1 expression was reduced in Vegf164-deficient embryos and knocked-down vegf levels enhanced the pharyngeal arch artery defects induced by tbx1 knockdown in zebrafish. Moreover, initial evidence suggested that a VEGF promoter haplotype was associated with an increased risk for cardiovascular birth defects in del22q11 individuals. These genetic data in mouse, fish and human indicate that VEGF is a modifier of cardiovascular birth defects in the del22q11 syndrome.