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PubMed2002

Mechanisms of myopia in Cohen syndrome mapped to chromosome 8q22.

PURPOSE: To analyze the mechanisms of myopia in Cohen syndrome (Mendelian Inheritance in Man [MIM] no. 216550). METHODS: A cross-sectional study of 22 Finnish patients (age range, 2-57 years) with Cohen syndrome, which maps to chromosome 8q22, was undertaken to record cycloplegic refraction, keratometry (corneal power and radius of curvature), biometry (anterior chamber depth [ACD], lens thickness [LT], axial [AL] and vitreal length [VL]), and Hoffer Q-modeled lens power. These components of refraction were correlated to age and spherical equivalent (SE) at the corneal plane. Contribution to total myopia of refractive (corneal and lenticular) and axial components was modeled by multiple linear regression and by estimating the effect of deviation from population mean values. RESULTS: The mean SE in patients with Cohen syndrome older than 10 years was -9.35 D; the mean cylinder power, +1.70 D; and the mean anisometropia, 0.53 D. Relative to the emmetropic eye of a young adult, the AL and VL (mean, 23.9 and 16.6 mm, respectively) and lens power (mean, 30.30 D) were higher in 74% and 93% of patients, respectively, and the ACD (mean, 2.5 mm) was smaller and the LT (mean, 4.9 mm) and corneal power (mean, 45.63 D) higher than average in all patients. Corneal power (r = 0.513, P = 0.021) increased with age, but AL and VL (P = 0.46 and 0.54, respectively) and lens power (P = 0.89) did not correlate with age. The lens power decreased with AL (r = -0.564, P = 0.029) and tended to increase with corneal power (r = 0.475, P = 0.074). Multiple linear regression identified AL and corneal power as independent predictors of SE. Based on deviation from population means, the lens power explained 55%, corneal power 23%, and AL 22% of total myopia. ACD decreased and LT increased markedly with age, rendering angle-closure glaucoma a possibility. CONCLUSIONS: Myopia in Cohen syndrome is mainly refractive in type and is due to high corneal and lenticular power, which is otherwise rare in young patients. It may be superimposed on axial myopia, probably related to polygenic factors that determine myopia in the general population. The refractive myopia in Cohen syndrome may result from dysgenesis and atrophy of the cornea, ciliary body, and iris, which in turn cause iridial and zonular laxity and spherophakia.

Abnormalities, Multiple↗
PubMed1994

Establishing a physical map of chromosome No. 4 of Plasmodium falciparum.

We isolated a panel of 20 DNA probes that hybridize specifically to chromosome No. 4 of Plasmodium falciparum and used them to construct a restriction map of chromosome No. 4 in the FCR3 strain. These probes were partially sequenced and had an insert size range of 70-310 bp (average 160 bp) and a GC content range of 19-53% (average 35%). Three probes were identical to previously described P. falciparum sequences. Two probes were homologous to an 18-bp repetitive sequence in a previously cloned P. falciparum gene but were not homologous to other parts of the gene. One probe sequence is a homologue of the heat shock protein, DnaJ. The location of these probes and four previously cloned probes on chromosome No. 4 were determined by using eight restriction enzymes that recognize 6-bp sites containing only G or C and 10 restriction enzymes that recognize 6-bp sites containing four G or C and two A or T. The locations of the probes were well distributed along the chromosome. Three probes were located at two sites and two probes were found at at least four sites on chromosome No. 4. Maps of chromosome No. 4 of the FCR3 strain, and three laboratory-selected, pyrimethamine-resistant derivative strains were constructed. Two of the strains, FCR3-D81 and FCR3-D85, each had two polymorphic forms of chromosome No. 4. Each of those polymorphic chromosomes had a duplicated part of the center of the chromosome making the cell diploid for the genetic material in that region. Those chromosomes also had an amplification and probable intrachromosomal translocation of a 50-kb fragment of chromosome No. 4. One strain derived from FCR3-D7, FCR3-D7-1 contained 20 copies of a tandemly amplified fragment carrying the dihydrofolate reductase-thymidylate synthase gene and an amplification of an unrelated part of the chromosome.

Animals↗
PubMed2005

A novel autosomal recessive non-syndromic deafness locus, DFNB66, maps to chromosome 6p21.2-22.3 in a large Tunisian consanguineous family.

Hereditary non-syndromic deafness is extremely heterogeneous. Autosomal recessive forms account for approximately 80% of genetic cases. Autosomal recessive non-syndromic sensorineural deafness segregating in a large consanguineous Tunisian family was mapped to chromosome 6p21.2-22.3. A maximum lod score of 5.36 at theta=0 was obtained for the polymorphic microsatellite marker IR2/IR4. Haplotype analysis defined a 16.5-Mb critical region between microsatellite markers D6S1602 and D6S1665. The screening of 3 candidate genes, COL11A2, BAK1 and TMHS, did not reveal any disease causing mutation, suggesting that this is a novel deafness locus, which has been named DFNB66. A search in the Human Cochlear EST Library for ESTs located in this critical interval allowed us to identify several candidates. Further investigations on these candidates are needed in order to identify the deafness-causing gene in this Tunisian family.

Chromosome Mapping↗
PubMed1996

The human lanosterol synthase gene maps to chromosome 21q22.3.

In order to contribute to the development of the transcriptional map of human chromosome 21 (HC21) we have used exon trapping to identify portions of HC21 genes. Using pools of random HC21-specific cosmids from the LL21NC02-Q library and cosmids from 21q22.3 we have identified five different coding regions with strong homology to the lanosterol synthase genes of rat and yeast. This enzyme catalyzes the cyclization of squalene-2,3-epoxide lanosterol, which is the parental compound of all steroids in mammals. Using somatic cell hybrids and HC21 yeast artificial chromosomes (YACS) and cosmids, we mapped the human lanosterol synthase cDNA gene to 2lq22.3 between markers D21S25 and 21qter. Cosmid Q7G8 from the LL21NC02-Q library and YAC 145D8 from the CEPH HC21 contig contain this human gene. We cloned a portion of the human lanosterol synthase cDNA (almost 85% of the coding region) from a brain cDNA library and determined its nucleotide sequence. The predicted human protein shows 83% identity to its rat and 40% to its yeast homolog. No obvious candidate human disease exists for lanosterol synthase deficiency and the role (if any) of triplication of this gene in the various phenotypes of trisomy 21 is unknown.

Amino Acid Sequence↗
PubMed1996

Human endothelin converting enzyme gene (ECE1) mapped to chromosomal region 1p36.1.

The chromosomal localization of the human endothelin converting enzyme gene (ECE1) has been identified. Southern blot analysis of human genomic DNA from human x mouse somatic cell hybrids demonstrated that ECE1 maps to chromosome 1. Fluorescence in situ hybridization of a digoxigenin-labeled human ECE1 probe to normal human metaphase chromosomes showed that the gene is located within chromosome band 1p36.1.

Animals↗
PubMed1992

A (CA)n repeat polymorphism for the human skeletal muscle alpha-actinin gene ACTN2 and its localization on the linkage map of chromosome 1.

A CA dinucleotide repeat polymorphism has been identified for the skeletal muscle alpha-actinin gene ACTN2. The observed heterozygosity is 44% (predicted heterozygosity 50%, PIC 0.47). This polymorphic marker has been localized between D1S74 and D1S103 on the multipoint linkage map of chromosome 1 at a position 44.4 cM from the most distal marker D1S68 at 1 qter.

Actinin↗
PubMed1991

The human kininogen gene (KNG) mapped to chromosome 3q26-qter by analysis of somatic cell hybrids using the polymerase chain reaction.

Kinins, peptide products of kininogens, may be involved in hypertensive and diabetic diseases, and inflammatory disorders. The human kininogen gene (KNG) has been mapped to chromosome 3, using a panel of human-hamster somatic cell hybrids by polymerase chain reaction of hybrid DNA with gene-specific primers. KNG was further assigned to 3q26-3qter, using DNA from a second panel of chromosome 3 deletion mapping cell hybrids.

Animals↗
PubMed1995

Detailed deletion mapping of chromosome 9p and p16 gene alterations in human borderline and invasive epithelial ovarian tumors.

We used PCR amplification of tandem repeats to study the pattern of allelic loss in borderline and invasive ovarian epithelial tumors using 12 primer pairs to generate a detailed deletion map of chromosome 9p. In the invasive ovarian carcinomas, there were three regions displaying high frequency of loss of heterozygosity (LOH) ranging from 31-38%. In contrast, LOH was a rare event among the borderline ovarian tumors, with one region revealing a rate of 20% and the remaining regions only 0-8% LOH. Therefore, allelic loss does not seem to be important for the development of borderline ovarian tumors. We also examined p16 gene expression and mutations in ovarian cancer cell lines and invasive and borderline ovarian tumor tissues. Southern blot analysis revealed no losses of the p16 gene in either the invasive or borderline ovarian tumors. However, the ovarian carcinoma cell lines showed a 50% homozygous deletion rate. SSCP analysis detected a mobility shift in only one (borderline) tumor. Since the primary invasive ovarian tumors did not show any deletions or mutations, it appears that p16 does not play a role in the pathogenesis of these tumors.

Carrier Proteins↗
PubMed1996

Saturation multipoint linkage mapping of chromosome 6q in type 1 diabetes.

Linkage analysis of type 1 diabetes sib pair families (n = 334) has suggested two separate regions of human chromosome 6q are linked to disease (designated IDDM5 and IDDM8). To test if these are false positive results, all available sib pair families (n = 429) were typed using a 92% informative map of chromosome 6q and multipoint analysis. The two regions still showed positive evidence of linkage, most notably the proterminal region, 6q27, corresponding to IDDM8 (MLS = 2.57, p = 0.0006; lambda s = 1.17). In addition, some evidence of transmission disequilibrium was seen with marker a046xa9 (IDDM5).

Chromosome Mapping↗
PubMed1996

A high resolution CEPH crossover mapping panel and integrated map of chromosome 11.

High resolution (0.1 cM) CEPH crossover mapping panels were constructed for chromosome 11. These panels will facilitate a transition from top-down physical and genetic mapping strategies to integrated breakpoint mapping strategies. Novel methods, which differ from other methods in overcoming the limitations of incomplete heterozygosity and variable marker density, were developed for creating the panels and integrated maps. This made it possible to identify and sublocalize the majority of crossovers in 61 families. The panels were used to map 139 microsatellite markers. A semi-integrated map and a fully-integrated map were constructed by combining these data with data from CEPH 7.1 and then integrating data from the radiation hybrid (RH) map. Genetic lengths estimated from the mapping panels were similar to the estimates obtained when all recombinant and non-recombinant offspring were included (189.4 cM in females and 126.1 cM in males), indicating that genetic distances are stable at this high marker density. The maps have a cM density of 0.62. The distance between ordered markers is 1.39-2.92 cM depending on the criterion for order and the extent of map integration. The 2D maps provide the resolution and flexibility needed to enhance current applications such as positional cloning and mapping complex disorders; while the mapping panels will greatly improve the resolution, reliability and efficiency of future genetic mapping.

Chromosome Mapping↗
PubMed1997

Gene locus for autosomal recessive distal myopathy with rimmed vacuoles maps to chromosome 9.

Distal myopathy with rimmed vacuoles is an autosomal recessive muscular disorder, characterized clinically by weakness of the distal muscles in the lower limbs in early adulthood. Recently, the gene locus for familial vacuolar myopathy with autosomal recessive inheritance (hereditary inclusion body myopathy) was mapped to chromosome 9 by genome-wide linkage analysis of nine Persian-Jewish families. Since both disease conditions share similar clinical, genetic, and histopathological features, we analyzed seven families with distal myopathy with rimmed vacuoles using ten microsatellite markers within the region of the hereditary inclusion body myopathy locus. Significantly high cumulative pairwise lod scores were obtained with three markers: D9S248 (Z(max) = 5.90 at theta = 0), D9S43 (Z(max) = 5.25 at theta = 0), and D9S50 (Z(max) = 4.23 at theta = 0). Detection of obligate recombination events as well as multipoint linkage analysis revealed that the most likely location of the distal myopathy with rimmed vacuoles gene is in a 23.3-cM interval defined by D9S319 and D9S276 on chromosome 9. The results raise the possibility that distal myopathy with rimmed vacuoles and hereditary inclusion body myopathy in Persian Jews are allelic diseases.

Adult↗
PubMed2003

Mapping of alpha- and beta-globin genes on Antarctic fish chromosomes by fluorescence in-situ hybridization.

The pathways and mechanisms of genomic change that have led to the peculiar haemoglobinless phenotype of the white-blooded Antarctic icefishes (16 species in the family Channichthyidae) constitute an important model for understanding the rapid diversification of the Antarctic notothenioid fish flock. To provide complementary structural information on genomic change at globin-gene loci in Antarctic fish species, cytogenetic studies and in-situ chromosomal mapping have been undertaken. Using a DNA probe containing one alpha- and one beta-globin gene from the embryonic/juvenile globin gene cluster of the red-blooded species Notothenia coriiceps, we mapped the cluster on the chromosomes of Antarctic teleosts by fluorescence in-situ hybridization. As anticipated on the basis of its molecular organization, the cluster was located on a single chromosome pair in all of the red-blooded fish species probed (N. coriiceps, N. angustata, Trematomus hansoni, T. pennellii). In contrast, the alpha/beta-globin probe did not recognize complementary sequences on the chromosomes of the white-blooded species Chionodraco hamatus and Channichthys rhinoceratus. These results represent the first example of chromosomal mapping of embryonic/juvenile globin genes in teleostean fishes. Beyond its relevance to the evolutionary history of Antarctic notothenioids, this work contributes to our understanding of the evolution of the chromosomal loci of globin genes in fishes and other vertebrates.

Animals↗
PubMed1985

Rearrangement of the genetic map of chromosome VII of Saccharomyces cerevisiae.

The genetic map of the right arm of chromosome VII of Saccharomyces cerevisiae includes markers on a distal segment for which meiotic linkage to the centromere-proximal marker cly8 has not previously been demonstrated. According to the currently accepted map, SUF4 is the most distal marker on the right arm. We have shown by tetrad analysis that SUF4 is linked to cly8 and ade6. The genetic distance between SUF4 and cly8 is 29 cM. These data indicate that the genetic map of the right arm of chromosome VII should be revised by inverting the orientation of the distal segment so that SUF4 is located near cly8, and SUC1 and MAL1 are the most distal markers. With this revision, all of the polymeric fermentation markers that have been mapped are located at the ends of chromosomes.

Chromosome Mapping↗
PubMed1993

The gene for creatine kinase, mitochondrial 2 (sarcomeric; CKMT2), maps to chromosome 5q13.3.

YAC clones for the creatine kinase, mitochondrial 2 (sarcomeric; CKMT2), gene were isolated. One of these YACs was localized on chromosome 5q13.3 by fluorescence in situ hybridization. A polymorphic dinucleotide repeat (heterozygosity 0.77) was identified within the seventh intron of the CKMT2 gene. Genotyping of CEPH families allowed positioning of CKMT2 on the multipoint map of chromosome 5 between D5S424 and D5S428, distal to spinal muscular atrophy (SMA) (5q12-q14).

Base Sequence↗