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PubMed1998

New Australian aboriginal complotypes characterised by increased C4 gene copy number.

Complement component C4 genes are located within the central region of the human MHC. The genomic arrangement of these genes is complex, with each chromosome usually encoding either one or two C4 genes. C4 allotyping of a group of Western Australian Aborigines demonstrated certain discrepancies in the densitometric ratios between the C4A4 and the C4A3 protein bands; however, the mechanism causing the increase in density of the C4A4 band was unknown. Our aim was to determine whether the increase in densitometry was due to an increase in the expression of the C4A4 isotype, or whether these individuals carried a new complotype characterised by an increased gene copy number. Using pulsed-field gel electrophoresis and Taq I RFLP analysis we will show that the apparent increase in C4A4 protein expression was due to the existence of new, previously uncharacterised Aboriginal complotypes defined by at least three C4 genes. Segregation analysis from an extensive family suggests that one of the new C4 complotypes is likely to contain the duplicated C4A4 isotype together with a C4B2 gene (C4A4, C4A4, C4B2) and is the first such chromosomal arrangement seen in this population group.

Australia↗
PubMedDate not supplied

Identifiability of segregation parameters using estimating equations.

To eliminate the need for distributional assumptions and to reduce the computational burden associated with the method of maximum likelihood, several researchers have proposed using estimating equations techniques for segregation analysis. One concern with the application of this technique has been that the first and second order moments may not carry sufficient information for identifying all of the parameters in segregation models. It is shown that in addition to the marginal means and covariances from nuclear family data, up to the third order product moments need to be used in estimating equations for identifying all of the segregation parameters in a major gene model. A polygenic component and potentially a common family environment parameter can also be identified using up to the fourth order moments. Two weighting functions are developed to improve statistical efficiency.

Environment↗
PubMed2001

Expression of the insulin receptor in the retina of the goldfish.

PURPOSE: Insulin is a peptide growth factor that is active in most tissues, both during development and in adulthood. The action of insulin is through its specific membrane receptor. Previously retinal progenitors in the adult goldfish were shown to proliferate vigorously when exposed to insulin in vitro.(1) The present study was undertaken to clone and characterize partial cDNAs that encode the goldfish's insulin receptor (IR) and to establish the cellular pattern of expression of this gene in the retina. METHODS: Standard methods were used for RNA isolation, reverse transcription-polymerase chain reaction, Northern blot analysis, and in situ hybridization. RESULTS: Multiple clones were isolated that, based on sequence analysis, segregated into two groups, presumed to represent two genes that encode the IR. These clones were designated goldfish IR-1 (gfIR-1) and goldfish IR-2 (gfIR-2). Northern blot analysis showed that both genes are expressed in multiple tissues, including the retina. Both gfIR-1 and -2 give rise to a single, major transcript, but the sizes of the two transcripts are different. In situ hybridizations using digoxygenin-labeled riboprobes showed that gfIR-1 and -2 are expressed by all differentiated retinal neurons as well as neuronal progenitors in the circumferential germinal zone. CONCLUSIONS: These data demonstrate that the IR is expressed in the retina of the goldfish, and, on the basis of the cellular pattern of expression, suggest that insulin may act both to regulate neurogenesis and influence the function of differentiated neurons. The cellular coexpression of the receptors for both insulin-like growth factor (IGF) 1 and insulin suggests that neurons and/or neuronal progenitors in the retina of the goldfish may contain hybrid IGF-1/insulin receptors.

Amino Acid Sequence↗
PubMed1991

[Load of hereditary diseases in the populations of the Adyg autonomic district].

Comparative analysis of the loads of hereditary diseases in two ethnically different populations coexisting in the Adyg national district was performed. The modes of inheritance of diseases studied were tested by segregational analysis. The results obtained demonstrated that the load of autosomal-recessive diseases in the populations of the Adyg national district is higher than that in Russian population, while the load of autosomal-dominant diseases is similar in two populations. This difference in the level of the loads appear to be connected with genetic structure of the populations studied. Regressional analysis of relations between loads and the level of inbreeding in the Adyg population showed the explicit interrelation between the load of autosomal-dominant diseases and the Fst correlation coefficient being 0.89.

Child↗
PubMed1999

Evidence for an ependymoma tumour suppressor gene in chromosome region 22pter-22q11.2.

Ependymomas are glial tumours of the brain and spinal cord. The most frequent genetic change in sporadic ependymoma is monosomy 22, suggesting the presence of an ependymoma tumour suppressor gene on that chromosome. Clustering of ependymomas has been reported to occur in some families. From an earlier study in a family in which four cousins developed an ependymoma, we concluded that an ependymoma-susceptibility gene, which is not the NF2 gene in 22q12, might be located on chromosome 22. To localize that gene, we performed a segregation analysis with chromosome 22 markers in this family. This analysis revealed that the susceptibility gene may be located proximal to marker D22S941 in 22pter-22q11.2. Comparative genomic hybridization showed that monosomy 22 was the sole detectable genetic aberration in the tumour of one of the patients. Loss of heterozygosity studies in that tumour revealed that, in accordance to Knudson's two-hit theory of tumorigenesis, the lost chromosome 22 originated from the parent presumed to have contributed the wild-type allele of the susceptibility gene. Thus, our segregation and tumour studies collectively indicate that an ependymoma tumour suppressor gene may be present in region 22pter-22q11.2.

Central Nervous System Neoplasms↗
PubMed1978

A clinical and genetic study of spinal muscular atrophy of adult onset: the autosomal recessive form as a discrete disease entity.

A clinical and genetic study of spinal muscular atrophy (SMA) of adult onset is reported. A genetic analysis of all cases of SMA occurring over a ten-year period in North-east England (48 index cases) has shown that chronic proximal SMA of adult onset is a distinct clinical and genetic entity, and is not a variant of the more common and relatively benign late juvenile cases. Nine cases of SMA of adult onset have been studied, occurring in 6 families. The median age of clinical onset was 35 years and the mean age at initial medical presentation was 37 years. The sex ratio was 5:4 (males:females). The condition is relatively benign and there is no evidence to date that life expectancy is shortened; there is usually no premonitory evidence of muscular weakness in early adult life. The muscular involvement is relatively symmetrical and the distal musculature is well preserved; clinical progression of the disease is interrupted by periods of apparent arrest. No patient was able to walk completely unaided twenty years after the initial clinical onset; the median age of patients in the study was 61 years but only one was confined to a wheelchair. In the early stages the recessive form of familial motor neuron disease must be excluded. A segregation analysis of sibs born after index cases was undertaken (segregation ratio of 0.20). This finding is consistent with autosomal recessive inheritance with an extended period during which the disease might initially present. The presence of new dominant mutations cannot be excluded, but is unlikely to account for more than 10% of cases. The carrier rate in the English population is estimated to be 1 in 300, with a gene frequency q = 0.00165. Prevalence is 0.32 per 100,000 in the general population. Empirical risks for genetic counselling are presented.

Adolescent↗
PubMed1989

Familial Mediterranean fever in Armenians: autosomal recessive inheritance with high gene frequency.

Familial Mediterranean fever (FMF) is a recurrent episodic inflammatory disorder of unknown pathogenesis that occurs with high frequency in non-Ashkenazi Jews and Armenians. However, there are some differences in the clinical manifestations of FMF in these ethnic groups. FMF has been reported to be an autosomal recessive disease in non-Ashkenazi Jews, with a male/female ratio of 1.7, indicating reduced penetrance in females. However, the inheritance is less clear for Armenians. To resolve this problem, we studied prospectively families of 64 Armenian index cases randomly ascertained at the UCLA FMF clinic. Fifty-three families containing 176 sibs in addition to the probands were analyzed by genetic segregation analysis (exclusions included: six single-child families, four families in which one of the parents was also affected, and a family with incomplete information). Upper and lower bounds of the segregation ratio were estimated, and ranged from .10 +/- .03 to .18 +/- .05 when only definitely affected sibs were classified as affected; .17 +/- .04 to .27 +/- .05 when considering "possibly affected" sibs as affected; and .19 +/- .04 to .30 +/- .05 when incomplete penetrance in females was corrected. A value of .25 is the expected segregation ratio for autosomal recessive inheritance, and our data are consistent with this mode of inheritance. We can reject autosomal dominant inheritance, where the expected segregation ratio is .5. Using extended pedigree data, we calculated an FMF gene frequency of 0.073 and a carrier rate of 1/7, which is about four times the frequency in non-Ashkenazi Jews.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Identification of a locus on chromosome 7q31, DFNB14, responsible for prelingual sensorineural non-syndromic deafness.

In our efforts to identify new loci responsible for non-syndromic autosomal recessive forms of deafness, DFNB loci, we have pursued the analysis of large consanguineous affected families living in geographically isolated areas. Here, we report on the study of a Lebanese family affected with a prelingual profound sensorineural isolated form of deafness. Segregation analysis resulted in a linkage with locus D7S554 to locus D7S2459 on 7q31, with a maximum lod score of 6.3. The causative gene was mapped to a 15 cM interval extending from D7S527 to D7S3074 (on the telomeric side). The distal limit of this interval could be located between D7S496 and D7S3074 which are the closest polymorphic loci flanking the gene underlying Pendred syndrome (PDS) on the centromeric and on the telomeric sides, respectively. To eliminate PDS as a candidate gene, its 21 exons were sequenced. No mutation was detected. This study therefore reports the identification of a novel locus, DFNB14, on chromosome 7q31, in a position proximal to PDS.

Audiometry↗
PubMed1998

A detailed linkage map of rainbow trout produced using doubled haploids.

We report the first detailed genetic linkage map of rainbow trout (Oncorhynchus mykiss). The segregation analysis was performed using 76 doubled haploid rainbow trout produced by androgenesis from a hybrid between the "OSU" and "Arlee" androgenetically derived homozygous lines. Four hundred and seventy-six markers segregated into 31 major linkage groups and 11 small groups (< 5 markers/group). The minimum genome size is estimated to be 2627.5 cM in length. The sex-determining locus segregated to a distal position on one of the linkage groups. We analyzed the chromosomal distribution of three classes of markers: (1) amplified fragment length polymorphisms, (2) variable number of tandem repeats, and (3) markers obtained using probes homologous to the 5' or 3' end of salmonid-specific small interspersed nuclear elements. Many of the first class of markers were clustered in regions that appear to correspond to centromeres. The second class of markers were more telomeric in distribution, and the third class were intermediate. Tetrasomic inheritance, apparently related to the tetraploid ancestry of salmonid fishes, was detected at one simple sequence repeat locus and suggested by the presence of one extremely large linkage group that appeared to consist of two smaller groups linked at their tips. The double haploid rainbow trout lines and linkage map present a foundation for further genomic studies.

Animals↗
PubMedDate not supplied

Assignment of ADA, ITPA, AK1, and AK2 to Chinese hamster chromosomes. Genetic and structural evidence for the conservation of mammalian autosomal synteny.

Interspecific somatic cell hybrids formed by fusion of mouse Cl1D cells with Chinese hamster primary spleen or fibroblast cells were used to form a clone panel with members retaining different combinations of Chinese hamster chromosomes and isozyme markers. Concordant segregation analysis of isozymes and chromosomes among clone panel members enabled the provisional assignment of ADA, ITPA, and AK1 to Chinese hamster chromosome 6. Diphtheria toxin selection for Chinese hamster chromosome 2 segregants in Dede cell X Cl1D somatic cell hybrids indicated AK2 is located on chromosome 2. These assignments extend observations of autosomal linkage group conservation in mammals--a concept further supported by similarity of G-band patterns in certain chromosomal regions bearing homologous loci in Chinese hamsters, humans, and mice.

Animals↗
PubMed1983

A genetic study of red blood cell zinc concentration in man.

Red blood cell zinc levels vary linearly with age within each sex. Age- and sex-adjusted zinc levels generated 6 familial correlations in nuclear families and twins. A simple additive polygenic model, with genetic heritability of zinc (h2) as the only unknown parameter, gave an excellent fit (X2(5) = 0.97, p greater than 0.96), with the corresponding estimate of h2 = 0.790 +/- 0.032. Commingling analysis supported the hypothesis that the logarithmic zinc values are approximately distributed according to a mixture of three normal distributions. Some support was found for a major gene hypothesis by complex segregation analysis under the mixed model. However, all the evidence came just from one family in which one of the 3 children's zinc value was over 3 standard deviations above the mean. When that family was excluded, there was no more evidence for a major gene. Under the most parsimonious mutlifactorial model that assumes equal heritabilities in children and adults, the heritability was estimated as 0.748 +/- 0.079, in good agreement with the outcome of path analysis. Biological interpretations are put forward and discussed.

Age Factors↗
PubMed2003

QTL mapping reveals a two-step model for the evolutionary reduction of inner microsporangia within the asteracean genus Microseris.

The reduction of inner (adaxial) pollen sacs (microsporangia, MS) as a diagnostic character for the three asteracean species, Microseris bigelovii, Microseris elegans and Microseris pygmaea, was analysed in an interspecific cross between Microseris douglasii and Microseris bigelovii with 4 MS and 2 MS, respectively, using the average number of MS per plant as a quantitative character. A previous QTL (Quantitative Trait Locus) analysis had revealed one major QTL (3B) and three modifier QTLs (3A, 4A, 7A) with epistatic effects only on the homozygous recessive 2 MS genotype of QTL 3B. Here we performed a bulked segregant analysis on four 2 MS and four 4 MS DNA-bulks with 407 EcoRI/ MseI AFLP-primer combinations each. In this way additional AFLP markers were mapped close to QTL 3B and QTL 3A. Three of them were converted to SCAR (Sequence Characterized Amplified region) markers. All markers were tested in natural populations of the disporangiate (2 MS) species M. bigelovii, M. elegans and M. pygmaea, and in different populations of tetrasporangiate (4 MS) M. douglasii. The marker distribution suggests that locus 3B mutated in a progenitor of the disporangiate species. QTL 3A has evolved in the 2 MS background of the major gene in the disporangiate species. Since M. pygmaea and M. bigelovii are the sister group to M. elegans, the 4 MS genotype for (markers of) QTL 3A in M. pygmaea populations is most likely due to a back mutation to the 4 MS state and could explain the slight instability of the 2 MS phenotype in this species.

Base Sequence↗
PubMed1994

Mapping of two new markers within the smallest interval harboring the spinal muscular atrophy locus by family and radiation hybrid analysis.

The locus responsible for the childhood-onset proximal spinal muscular atrophies (SMA) has recently been mapped to an area of 2-3 Mb in the region q12-q13.3 of chromosome 5. We have used a series of radiation hybrids (RHs) containing distinct parts of the SMA region as defined by reference markers. A cosmid library was constructed from one RH. Thirteen clones were isolated and five of these were mapped within the SMA region. Both RH mapping and fluorescence in situ hybridization analysis showed that two clones map in the region between loci D5S125 and D5S351. One of the cosmids contains expressed sequences. Polymorphic dinucleotide repeats were identified in both clones and used for segregation analysis of key recombinant SMA families. One recombination between the SMA locus and the new marker 9Ic (D5S685) indicates that 9Ic is probably the closest distal marker. The absence of recombination between the SMA locus and marker Fc (D5S684) suggests that Fc is located close to the disease gene. These new loci should refine linkage analysis in SMA family studies and may facilitate the isolation of the disease gene.

Animals↗
PubMed1991

Exclusion of linkage between the collagenase gene and generalized recessive dystrophic epidermolysis bullosa phenotype.

Generalized recessive dystrophic epidermolysis bullosa (RDEB) is a severe inherited autosomal disease characterized by dermolytic blister formation. Enhanced collagenase and/or abnormal collagenase have been reported in skin from affected patients, suggesting that collagenase could be responsible for the absence of anchoring fibrils in this disorder. We used a genetic linkage approach to test the hypothesis that this disease is due to a defect in the collagenase gene in nine affected families. Analysis of amplified genomic DNA fragments of the collagenase gene by means of denaturing gradient gel electrophoresis (DGGE) allowed us to detect intragenic polymorphisms, which were subsequently characterized by direct genomic sequencing. Segregation analysis of these polymorphic sites showed exclusion of linkage between the collagenase gene and generalized RDEB phenotype in a family with consanguineous parents and three affected children. However, the possibility of linkage with the collagenase gene in the other eight families tested could not be excluded. The genetic markers described here provide a tool for investigating genetic linkage in other affected families. Overall, our results show that generalized RDEB can be caused by a defect in a gene other than the collagenase gene, and support the hypothesis that the genetic defect lies in abnormal anchoring fibril formation.

Base Sequence↗
PubMed2004

Molecular mapping of Stb1, a potentially durable gene for resistance to septoria tritici blotch in wheat.

Septoria tritici blotch (STB), caused by the ascomycete Mycosphaerella graminicola (anamorph Septoria tritici), was the most destructive disease of wheat in Indiana and adjacent states before deployment of the resistance gene Stb1 during the early 1970s. Since then, Stb1 has provided durable protection against STB in widely grown wheat cultivars. However, its chromosomal location and allelic relationships to most other STB genes are not known, so the molecular mapping of Stb1 is of great interest. Genetic analyses and molecular mapping were performed for two mapping populations. A total of 148 F1 plants (mapping population I) were derived from a three-way cross between the resistant line P881072-75-1 and the susceptible lines P881072-75-2 and Monon, and 106 F6 recombinant-inbred lines (mapping population II) were developed from a cross between the resistant line 72626E2-12-9-1 and the susceptible cultivar Arthur. Bulked-segregant analysis with random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), and microsatellite or simple-sequence repeat (SSR) markers was conducted to identify those that were putatively linked to the Stb1 gene. Segregation analyses confirmed that a single dominant gene controls the resistance to M. graminicola in each mapping population. Two RAPD markers, G7(1200) and H19(520), were tightly linked to Stb1 in wheat line P881072-75-1 at distances of less than 0.68 cM and 1.4 cM, respectively. In mapping population II, the most closely linked marker was SSR Xbarc74, which was 2.8 cM proximal to Stb1 on chromosome 5BL. Microsatellite loci Xgwm335 and Xgwm213 also were proximal to Stb1 at distances of 7.4 cM and 8.3 cM, respectively. The flanking AFLP marker, EcoRI-AGC/ MseI-CTA-1, was 8.4 cM distal to Stb1. The two RAPD markers, G7(1200) and H19(520), and AFLP EcoRI-AGC/ MseI-CTA-1, were cloned and sequenced for conversion into sequence-characterized amplified region (SCAR) markers. Only RAPD allele H19(520) could be converted successfully, and none of the SCAR markers was diagnostic for the Stb1 locus. Analysis of SSR and the original RAPD primers on several 5BL deletion stocks positioned the Stb1 locus in the region delineated by chromosome breakpoints at fraction lengths 0.59 and 0.75. The molecular markers tightly linked to Stb1 could be useful for marker-assisted selection and for pyramiding of Stb1 with other genes for resistance to M. graminicola in wheat.

Ascomycota↗
PubMed1993

Multivariate genetic analysis of apo AI concentration and HDL subfractions: evidence for major locus pleiotropy.

A major locus influencing apolipoprotein AI (apo AI) serum levels was detected using data from the Donner Laboratory Family Study. This locus accounts for 46% of the phenotypic variability in apo AI levels. Multivariate segregation analysis revealed that this major locus also has significant pleiotropic effects on the relative distribution of high density lipoproteins.

Apolipoprotein A-I↗
PubMed1985

Regional assignment of the genes for TK1, GALK, ALDC, and ESD on chromosome 8 in the American mink by chromosome-mediated gene transfer.

A panel of clones of mink-Chinese hamster somatic cell hybrids was analysed to obtain data for assigning the genes for thymidine kinase-1 (TK1), galactokinase (GALK), subunit C of aldolase (ALDC), and esterase D (ESD) to specific mink chromosomes. The results demonstrate that the genes for TK1, GALK, ALDC and ESD are syntenic and located on mink chromosome 8. Prometaphase analysis of transformed mouse cells obtained by transfer of mink genes by means of metaphase chromosomes demonstrated the presence of mink chromosome 8 fragments of different sizes in some of the independent transformants. Segregation analysis of these fragments and mink TK1, GALK, ALDC and ESD allowed us to assign the genes for TK1 and GALK to 8p24, ALDC to pter-8p25, and ESD to 8q24-8qter.

Animals↗
PubMedDate not supplied

Familial resemblance of alcohol consumption levels in Jewish families.

The role of genetic and environmental factors determining the variability in alcohol consumption levels was investigated in 68 families ascertained through heroin-dependent Jewish male probands. Sibling correlations for peak weekly alcohol consumption ranged from 0.22 to 0.32, with limited changes on adjustment for sex, age and environmental variables. The parent-child correlations were relatively low. Segregation analysis indicated that a major effect of a non-transmitted environmental factor explained the mixture of distributions. There was no evidence for a polygenic effect on alcohol consumption in the families. When segregation models were fitted to sex, age and environment-adjusted alcohol levels, the mixed environment model was rejected, whereas the mixed genetic model was not. These findings are consistent with two previously published segregation analyses of alcohol dependence, and further highlight the heterogeneous aetiology and transmission of alcohol consumption and alcohol dependence.

Adult↗