RESUMO
We have examined the linkage of two new polymorphic DNA markers (D19S62 and D19S63) and a previously unreported polymorphism with an existing DNA marker (ERCC1) to the myotonic dystrophy (DM) locus. In addition, we have used pulsed-field gel electrophoresis to obtain a fine-structure map of this region. The detection of linkage disequilibrium between DM and one of these markers (D19S63) is the first demonstration of this phenomenon in a heterogeneous DM population. The results suggest that at least 58% of DM patients in the British population, as well as those in a French-Canadian subpopulation, are descended from the same ancestral DM mutation. We discuss the implications of this finding in terms of strategies for cloning the DM gene, for a possible role in modification of risk for prenatal and presymptomatic testing, and we speculate on the origin and number of existing mutations which may result in a DM phenotype.
Assuntos
Cromossomos Humanos Par 19 , Marcadores Genéticos , Desequilíbrio de Ligação/genética , Distrofia Miotônica/genética , Polimorfismo Genético , Genótipo , Humanos , SoftwareRESUMO
We have constructed and analysed somatic cell hybrids from cell lines containing balanced reciprocal translocations involving chromosome 19 and providing two new breakpoints on 19q. These and other hybrids have been tested with a series of markers from 19q to enhance the existing map. Several new cloned DNA sequences that map to 19q13.3-19qter are reported; the locus D19Z1 has been analysed by CHEF gel electrophoresis.
Assuntos
Mapeamento Cromossômico , Cromossomos Humanos Par 19 , Animais , Aberrações Cromossômicas , Transtornos Cromossômicos , Fragilidade Cromossômica , Cricetinae , Eletroforese em Gel de Ágar , Marcadores Genéticos , Humanos , Células Híbridas , Cariotipagem , Camundongos , Hibridização de Ácido Nucleico , Translocação GenéticaRESUMO
The order of fourteen polymorphic markers localised to the long arm of human chromosome 19 has been established by multipoint mapping in a set of 40 CEPH (Centre d'Etude de Polymorphisme Humain, Paris) reference families. We report here the linkage relationship of the myotonic dystrophy (DM) locus to twelve of these markers as studied in 45 families with DM. The resulting genetic map is supported by the localisation of the DNA markers in a panel of somatic cell hybrids. Ten of the twelve markers have been shown to be proximal to the DM gene and two, PRKCG and D19S22, distal but at distances of approximately 25 cM and 15 cM, respectively. The closest proximal markers are APOC2 (apolipoprotein C-II) and CKM (creatine kinase, muscle) approximately 3 cM and 2 cM from the DM gene respectively, in the order APOC2-CKM-DM. The distance between APOC2, CKM and DM (of the order of 2 million base pairs) and their known orientation should permit directional chromosome walking and jumping. The data presented here should enable us to determine whether or not new markers are distal to APOC2/CKM and thus potentially flank the DM gene.
Assuntos
Cromossomos Humanos Par 19 , Distrofia Miotônica/genética , Polimorfismo Genético , Bandeamento Cromossômico , Mapeamento Cromossômico , Sondas de DNA , Ligação Genética , Marcadores Genéticos , Humanos , Células Híbridas , Linhagem , Recombinação GenéticaRESUMO
The most useful markers for the prenatal diagnosis of myotonic dystrophy (DM) are APOC2 and CKM, both of which map proximal to DM. In order to produce other markers useful for DM, we have screened genomic DNA libraries constructed from cell line 20XP3542-1-4, which contains 20 to 30 Mb of human material including APOC2 and CKM. Of 51 human clones identified, seven map to chromosome 17, four to chromosome 8, and nine to chromosome 19, and the remaining 31 were excluded form chromosome 19 but not localised further. Four of the clones from chromosome 19 map distal to CKM and two of these clones (D19S62 and D19S63) are closely linked to DM. Analysis of a family in which a crossover between CKM and DM has occurred shows that neither D19S62 nor D19S63 and DM have recombined, suggesting that D19S62 and D19S63 are either closer to or flanking DM in relation to CKM. Pulsed field gel analysis showed that CKM, D19S62, and D19S63 map to a region of at least 1500 kb.
Assuntos
Cromossomos Humanos Par 19 , Marcadores Genéticos , Distrofia Miotônica/genética , Polimorfismo de Fragmento de Restrição , Southern Blotting , Clonagem Molecular/métodos , DNA/análise , Eletroforese em Gel de Ágar , Ligação Genética , Humanos , Hibridização de Ácido Nucleico , LinhagemRESUMO
We have studied the genetic linkage of two markers, the apolipoprotein C1 (APOC1) gene and a cytochrome P450 (CYP2A) gene, in relation to the gene for myotonic dystrophy (DM). A peak lod score of 9.29 at 2 cM was observed for APOC1-DM, with a lod score of 8.55 at 4 cM for CYP2A-DM. These two markers also show close linkage to each other (theta max = 0.05, Zmax = 9.09). From examination of the genotypes of the recombinant individuals, CYP2A appears to map proximal to DM because in one recombinant individual CYP2A, APOC2 and CKMM had all recombined with DM. Evidence from another CYP2A-DM recombinant individual places CYP2A proximal to APOC2 and CKMM. Localisation of CYP2A on a panel of somatic cell hybrids also suggests that it is proximal to DM and APOC2/C1/E gene cluster.
Assuntos
Apolipoproteínas C/genética , Sistema Enzimático do Citocromo P-450/genética , Distrofia Miotônica/genética , Apolipoproteína C-I , Mapeamento Cromossômico , Cromossomos Humanos Par 19 , Feminino , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Ligação Genética , Marcadores Genéticos , Humanos , Células Híbridas , Masculino , Linhagem , Fenobarbital/farmacologia , Polimorfismo de Fragmento de RestriçãoRESUMO
The gene coding for a Na+,K+-ATPase alpha subunit (ATP1A3) has been localized to the q12----q13.2 region of human chromosome 19, potentially close to the myotonic dystrophy (DM) gene. In view of previous studies implicating a Na+,K+-ATPase in the pathology of DM, we have examined the possibility that ATP1A3 is a candidate for the DM locus. Although linked, several clear instances of recombination between ATP1A3 and DM rule out the possibility that mutations in ATP1A3 cause the disease. Examination of multiply informative pedigrees indicates the gene order DM-APOC2-ATP1A3.
