Human interferon gamma receptor 1 (IFNGR1) gene maps to chromosome region 6q23–6q24

Summary The human interferon receptor (IFNGR1) gene has been localized by in situ hybridization to chromosome 6 at q23–q24. This chromosomal region is often deleted in lymphoid cell malignancies.     

Trophoblast glycoprotein recognised by monoclonal antibody 5T4 maps to human chromosome 6q14–q15

Summary Human × rodent hybrids were stained by indirect immunofluorescence with 5T4, a murine monoclonal antibody that recognises a 72 kdalton glycoprotein expressed by human trophoblasts and a very restricted range of adult tissues; they were analysed by flow cytometry. Concordance analysis supported by segregation data allowed assignment of the gene controlling glycoprotein expression (M6P1) to chromosome 6. Similar analysis with translocation hybrids gave a regional assignment to 6q14–q15. M6P1 is distinct from NT5, coding for 5 nucleotidase, which maps to the same region.     

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.     

A locus for familial generalized lentiginosis without systemic involvement maps to chromosome 4q21.1–q22.3

Generalized lentiginosis (GL) is characterized by widespread lentigines without associated noncutaneous abnormalities. In this study we performed a genome-wide linkage search in a Chinese family with GL and localized the familial GL locus to chromosome 4q21.1–q22.3, with a maximum two-point LOD score of 3.01 for D4S395 and D4S423 at a recombination fraction of 0. Multipoint analysis (maximum LOD score of 5.08 between markers D4S395 and D4S1563) and haplotype construction showed strong evidence of linkage in a region of 20 Mb flanked by markers D4S2915 and D4S1560 on chromosome 4q21.1–q22.3. This is the first report of linkage for GL, and it will provide further insight into the controversy of whether GL is an entity distinct from LEOPARD syndrome.Qinghe Xing and Xiangdong Chen contributed equally to this work     

A gene responsible for Ghosal hemato-diaphyseal dysplasia maps to chromosome 7q33–34

Ghosal hemato-diaphyseal dysplasia is a rare autosomal recessive disorder characterized by a progressive sclerosing diaphyseal dysplasia and refractory anemia. The pathogenesis and genetic bases of this syndrome remain hitherto unknown. We have performed a genome wide search in two inbred families originating from Algeria and Tunisia. Here, we report on the mapping of a disease gene to chromosome 7q33–34 (Z _max = 4.21 at θ = 0 at locus D7S2513) in a 3.4 Mb defined by loci D7S2560 and AC091742. Ongoing studies will hopefully lead to identification of the disease-causing gene.     

Congenital, low penetrance lymphedema of lower limbs maps to chromosome 6q16.2–q22.1 in an inbred Pakistani family

Hereditary lymphedema is a rare, lymphatic disorder resulting in the chronic swelling of the extremities. It shows wide inter- and intra-familial clinical heterogeneity as well as variability in the age of onset. There are more than four genetically distinct lymphedema conditions known and mutations in three genes have been discovered in families with lymphedema. However, many other familial lymphedemas do not show linkage with the known loci, suggesting genetic heterogeneity. Here, we describe a large inbred Pakistani family with congenital, progressive lymphedema confined to the lower limbs, which fades away at 40–45 years of age. This condition segregates in an autosomal dominant fashion with reduced penetrance. The features are close to primary lymphedema I, Nonne–Milory type (MIM 153100). We exclude this condition for linkage to the known loci for lymphedema by employing highly polymorphic microsatellite markers from these intervals. Then, through a genome-wide linkage study we show that the malformation in our family maps to chromosome 6q16.2–q22.1. The highest pair-wise LOD score (Z _max = 3.19) was obtained with microsatellite marker D6S1671, and a multipoint score of 3.75 was obtained at 108 cM. Haplotype analysis indicated that the critical interval in this family flanks between markers D6S1716 and D6S303. Mutation analysis in FOXO3, a likely candidate within this interval, did not show any pathogenic change in the affected family subjects. Our study provides an evidence of a second locus for lymphedema type I. The discovery of the underlying gene could be helpful for the understanding of this heterogeneous hereditary condition.     

Regional localization of human ecto-5′nucleotidase to chromosome 6q14–q21

Summary Human and mouse hybrids that contain fragments of human chromosome 6 as translocations were analysed for expression of ecto-5nucleotidase enzymic activity measured by the conversion of AMP to adenosine and for antigenicity recognized by a monoclonal antibody specific for the human isozyme. Both methods allow a regional assignment of ecto-5nucleotidase to 6q14–q21.     

The polymorphic Fcγ receptor II gene maps to human chromosome 1q

Human receptors for IgG (FcR) play important roles in the immune response. Expression of the human FcRII gene may be relevant in immune complex related disorders such as systemic lupus erythematosus and Sjogren's syndrome. We have used spot blot analysis of dual laser-sorted human chromosomes to localize the FcRII gene to human chromosome 1. Spot blot analysis of sorted derivative chromosomes sublocalized the gene to the chromosome 1 long arm (1q1225.1). This subchromosomal localization involved reassigning a reciprocal chromosome translocation breakpoint. We also identified Xmn I and Taq I FcRII polymorphic restriction sites that arose before the races diverged. These common Xmn I and Taq I polymorphisms are predicted to be informative for segregation analysis with human diseases in 85% of all matings.     

The apolipoprotein(a) gene resides on human chromosome 6q26–27, in close proximity to the homologous gene for plasminogen

Summary Apolipoprotein(a) [apo(a)], the glycoprotein associated with the lipoprotein(a) [Lp(a)] subfraction of plasma lipoproteins, has been shown to exhibit heritable molecular weight isoforms ranging from 400–700 kDa. Increased serum concentrations of Lp(a) correlate positively with the risk of atherosclerosis. Variations in Lp(a) plasma levels among individuals are inherited as a codominant quantitative trait. As part of an effect to define the basis of these variations and further clarify the expression of the protein, we have determined the chromosomal location of the human apo(a) gene. Blot hybridization analysis of DNA from a panel of mouse-human somatic cell hybrids with an apo(a) cDNA probe revealed a complex pattern of bands, all of which segregated with chromosome 6. In situ hybridization yielded a single peak of grain density located on chromosome 6q26–27. Apo(a) cDNA sequences exhibit striking homology to those of the plasma protease plasminogen, and, therefore, we have reexamined the chromosome assignment of the plasminogen gene. We conclude that both the apo(a) and plasminogen genes reside on human chromosome 6q22–27, consistent with a gene duplication mechanism for their evolutionary origin. The results are of significance for the genetic control of apo(a) expression and genetic influences predisposing to atherosclerosis.     

A locus for juvenile myoclonic epilepsy maps to 2q33–q36

We performed a whole genome linkage analysis in a three-generation south Indian family with multiple members affected with juvenile myoclonic epilepsy (JME). The maximum two-point LOD score obtained was 3.32 at recombination fraction (θ) = 0 for D2S2248. The highest multipoint score of 3.59 was observed for the genomic interval between D2S2322 and D2S2228 at the chromosomal region 2q33–q36. Proximal and distal boundaries of the critical genetic interval were defined by D2S116 and D2S2390, respectively. A 24-Mb haplotype was found to co-segregate with JME in the family. While any potentially causative variant in the functional candidate genes, SLC4A3, SLC23A3, SLC11A1 and KCNE4, was not detected, we propose to examine brain-expressed NRP2, MAP2, PAX3, GPR1, TNS1 and DNPEP, and other such positional candidate genes to identify the disease-causing gene for the disorder.     

The gene encoding the large human neurofilament subunit (NF-H) maps to the q121–q131 region on human chromosome 22

Summary Using a rat cDNA probe encoding for the C-terminal textension of the large neurofilament subunit (NF-H), we have assigned, by in situ hybridization, the human NF-H gene to the q121–q131 region of chromosome 22. This localization may have implications in neurological diseases such as meningioma where a recessive locus involved in oncogenesis is located within this region.     

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.     

A novel locus for autosomal dominant nonsyndromic hearing loss (DFNA44) maps to chromosome 3q28–29

Hereditary non-syndromic sensorineural hearing loss (NSSHL) is a genetically highly heterogeneous group of disorders. Autosomal dominant forms account for up to 20% of cases. To date, 39 loci have been identified by linkage analysis of affected families that segregate NSSHL forms in the autosomal dominant mode (DFNA). Investigation of a large Spanish pedigree with autosomal dominant inheritance of bilateral and progressive NSSHL of postlingual onset excluded linkage to known DFNA loci and, in a subsequent genome-wide scan, the disorder locus was mapped to 3q28-29. A maximum two-point LOD score of 4.36 at theta=0 was obtained for marker D3S1601. Haplotype analysis placed the novel locus, DFNA44, within a 3-cM genetic interval defined by markers D3S1314 and D3S2418. Heteroduplex analysis and DNA sequencing of coding regions and exon/intron boundaries of two genes (CLDN16 and FGF12) in this interval did not reveal disease-causing mutations.     

A syndromic form of autosomal recessive congenital microcephaly (Jawad syndrome) maps to chromosome 18p11.22–q11.2

We report a consanguineous Pakistani family with seven affected individuals showing a syndromic form of congenital microcephaly. Clinical features of affected individuals include congenital microcephaly with sharply slopping forehead, moderate to severe mental retardation, anonychia congenita, and digital malformations. By screening human genome with microsatellite markers, this autosomal recessive condition was mapped to a 25.2 cM interval between markers D18S1150 and D18S1100 on chromosome 18p11.22–q12.3. However, the region of continuous homozygosity between markers D18S1150 and D18S997 spanning 15.33 cM, probably define the most likely candidate region for this condition. This region encompasses a physical distance of 12.03 Mb. The highest two-point LOD score of 3.03 was obtained with a marker D18S1104 and multipoint score reached a maximum of 3.43 with several markers. Six candidate genes, CEP76, ESCO1, SEH1L, TUBB6, ZNF519, and PTPN2 were sequenced, and were found to be negative for functional sequence variants.     

A locus for autosomal dominant accessory auricular anomaly maps to 14q11.2–q12

Accessory auricular anomaly is a small excrescence of skin that contains elastic cartilage on different regions of the helix and the face. Previous work has shown that the genetic trait of some patients with the isolated symptom of accessory auricular anomaly is autosomal dominant. To map the gene for autosomal dominant accessory auricular anomaly (ADAAA), we investigated a Chinese family with 11 affected individuals. We performed linkage analysis with microsatellite markers spanning the whole human-genome in the family. The inheritance pattern of the ADAAA family was autosomal dominant with complete penetrance. Two-point linkage analysis revealed significant maximum LOD scores of 4.20(D14S990 and D14S264, sita = 0) in the family. Haplotype construction and multipoint linkage analysis also confirmed the locus and defined the isolated ADAAA locus to a 9.84 cM interval between the markers D14S283 and D14S297. Our study assigned an isolated ADAAA locus to 14q11.2–q12. This is the first ADAAA locus reported to date.Y. Yang and J. Guo contribute to this work equally.     

Human zinc finger gene ZNF23 (Kox16) maps to a zinc finger gene cluster on chromosome 16q22, and ZNF32 (Kox30) to chromosome region 10q23-–q24

Two members of the KOX gene family, ZNF23 (KOX16) and ZNF32 (KOX30), have been mapped by in situ hybridization to chromosome regions 16q22 and 10q23-q24, respectively. The map location of ZNF23 and ZNF32 placed these zinc finger protein genes near to chromosome loci that, under certain in vitro conditions, are expressed as fragile sites (FRA16B, FRA16C) and (FRA10D, FRA10A, FRA10B and FRA10E). Human zinc finger gene ZNF32 maps to a chromosome region on 10q23-24 in which deletions have been observed associated with malignant lymphoma on 10q22-23 and with carcinoma of the prostate on 10q24. ZNF23 is located on 16q22 in a chromosomal region that has been involved in chromosome alterations characteristic of acute myeloid leukemia. A second Kox zinc finger gene (ZNF19/KOX12) was recently mapped to the same chromosome region on human chromosome 16q22. In the analogous murine position, the murine zinc finger genes Zfp-1 and Zfp-4 are found in the syntenic 16q region of mouse chromosome 8. Thus, ZNF19 and ZNF23 might be members of an evolutionarily conserved zinc finger gene cluster located on human chromosome 16q22.     

Assignment of the gene for carboxypeptidase A to human chromosome 7q22→qter and to mouse chromosome 6

Summary A rat cDNA probe for preprocarboxypeptidase A was used to follow the segregation of the human gene for carboxypeptidase A (CPA) in 49 human x mouse somatic cell hybrids using Southern filter hybridization techniques. CPA was assigned to human chromosome 7q22qter. Similarly, the probe was used to follow the segregation of the mouse gene for carboxypeptidase A (Cpa) in 19 mouse x Chinese hamster somatic cell hybrids. Cpa was assigned to mouse chromosome 6. The gene for carboxypeptidase A forms part of a syntenic group that is conserved in man and mouse.Preliminary chromosomal assignments of carboxypeptidase A in man and mouse have been made in abstract (Honey et al. 1983a, b)     

A novel locus for Usher syndrome type I, USH1G, maps to chromosome 17q24–25

Usher syndrome (USH) is an autosomal recessive disorder associated with sensorineural hearing impairment and progressive visual loss attributable to retinitis pigmentosa. This syndrome is both clinically and genetically heterogeneous. Three clinical types have been described of which type I (USH1) is the most severe. Six USH1 loci have been identified. We report a Palestinian consanguineous family from Jordan with three affected children. In view of the combination of profound hearing loss, vestibular dysfunction, and retinitis pigmentosa in the patients, we classified the disease as USH1. Linkage analysis excluded the involvement of any of the known USH1 loci. A genome-wide screening allowed us to map this novel locus, USH1G, in a 23-cM interval on chromosome 17q24-25. The USH1G interval overlaps the intervals for two dominant forms of isolated hearing loss, namely DFNA20 and DFNA26. Since several examples have been reported of syndromic and isolated forms of deafness being allelic, USH1G, DFNA20, and DFNA26 might result from alterations of the same gene. Finally, a mouse mutant, jackson shaker ( js), with deafness and circling behavior has been mapped to the murine homologous region on chromosome 11.     

The gene coding for the α-chain of human propionyl-CoA carboxylase maps to chromosome band 13q32

Summary The human gene encoding the -polypeptide of propionyl-CoA carboxylase (PCC) has hitherto been localized to the distal half of the long arm of chromosome 13, segment 13q22q34. We studied the enzyme activities of mitochondrial carboxylases in cell cultures obtained from patients with different deletions of chromosome 13. By setting the PCC activity in normal diploid cell cultures (control group) at 100%, cell cultures with trisomy 13 showed 150% activity. In contrast, one of four patients with partial monosomy 13 had an enzyme activity of only 50%. Thus, by comparative deletion mapping, combined with studies of the gene-dosage effect, we have been able to assign the PCCA gene locus to chromosome band 13q32.     

Apoptosis regulatory gene NEDD2 maps to human chromosome segment 7q34–35, a region frequently affected in haematological neoplasms

Developmentally regulated mouse gene Nedd2 encodes a protein similar to the product of the nematode Caenorhabditis elegans cell death gene ced-3 and the mammalian interleukin-1-converting enzyme. Overexpression of Nedd2 in cultured mammalian cells induces apoptosis that can be blocked by proto-oncogene BCL2. We have isolated cDNA clones for the human homologue of the mouse gene and, by using these as probes, mapped the human NEDD2 gene to 7q34-35 by fluorescence in situ hybridisation. The potential tumour suppressor function of NEDD2 is discussed.