FIG 1 - uploaded by Michael Hayden
Content may be subject to copyright.
-Partial karyotypes of prometaphase chromosomes of (A, top) patient 1, (B, bottom) patient 2. On the left sides of both A and B, idiogrammatic representations of the normal 4 and deleted 4 are shown. On the right sides ofboth A and B, the normal 4 and the deleted 4 are marked. Patient 1 and patient 2 have nonoverlapping interstitial deletions of 4p.
Source publication
The linked DNA marker for Huntington disease has recently been mapped to the short arm of chromosome 4 by somatic cell hybridization studies. Southern blot analysis of DNA from patients with Wolf-Hirschhorn syndrome (WHS) has suggested that the linked marker maps within the terminal 4p16 band. We have now accomplished subregional assignment of G8 (...
Contexts in source publication
Context 1
... oper, and chromosomes were studied following Wright's staining. More than 50 cells from both patients and controls were analyzed. Patient 1 has the typical Wolf-Hirschhorn phenotype and the karyotype 46, XX, del(4)(pl6.lpl6.3). All of band 4pl6.2 is absent together with the distal segment of 4p16. 1 and possibly proximal segment of 4p16.3 ( fig. 1A). Patient 2 has mental retarda- tion, no growth retardation, and multiple minor anomalies, lacks the Wolf-Hirschhorn phenotype [4], and has the karyotype 46,XX,del(4)(pl4 p15.32), (fig. 1B). Thus, both patients have nonoverlapping interstitial deletions of ...
Context 2
... situ hybridization of 3H-labeled pK082, a subclone of G8, was performed on meta- phase chromosomes of these two patients and a normal control using probe concentra- tions ranging from 50 to 200 ng/ml of hybridization solution. Specific activities ranged from 9.5 x 106 to 1.4 x 107 cpm/[ug DNA. Hybridization was allowed to proceed at 37TC for 12-16 hrs, and exposure time in Kodak Nuclear Track Emulsion Type NTB2 at 4TC ranged from 12 to 21 days. This was followed by development in DEKTOL devel- oper, and chromosomes were studied following Wright's staining. More than 50 cells from both patients and controls were analyzed. Patient 1 has the typical Wolf-Hirschhorn phenotype and the karyotype 46, XX, del(4)(pl6.lpl6.3). All of band 4pl6.2 is absent together with the distal segment of 4p16. 1 and possibly proximal segment of 4p16.3 ( fig. 1A). Patient 2 has mental retarda- tion, no growth retardation, and multiple minor anomalies, lacks the Wolf-Hirschhorn phenotype [4], and has the karyotype 46,XX,del(4)(pl4 p15.32), (fig. 1B). Thus, both patients have nonoverlapping interstitial deletions of ...
Similar publications
We report the clinical and cytogenetic findings in a family in which a balanced reciprocal translocation between the long arm of chromosome 4 and the short arm of chromosome 5 is segregating together with Huntington disease in 2 generations. In situ hybridization studies revealed that the linked human DNA marker is located on the short arm of the n...
Citations
... HD is an autosomal, dominantly inherited neuropsychiatric and movement disorder. An unstable (CAG) n repeat region within the coding exon 1 of the IT15 gene (also known as huntingtin), localized on the short arm of chromosome 4 (4p16.3), is responsible for HD (4,5). The variable number of (CAG) n repeats is related to different alleles and phenotypes. ...
Expansion of an unstable trinucleotide (CAG)n repeat region within exon 1 of the gene IT15 causes autosomal, dominantly inherited Huntington's disease (HD). The number of CAG-repeats varies from 6 to 35 in normal
individuals, whereas in affected patients the expanded allele contains 40 or more CAG-repeats. Thus, exact determination of
both alleles of the gene (normal and expanded) on the molecular level is of great importance for clinical diagnosis and prognosis
regarding the course of the disease. In our study, we optimized and evaluated a highly sensitive, automated, and economical
molecular method for length characterization of the trinucleotide fragment expansion such as (CAG)n repeat region based on ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC). We found that IP-RP-HPLC
can be used for exact fragment length measuring between 60-280 bp as a sensitive and advantageous alternative method to conventional
techniques.
... Received August 19, 1991 revision received October 14, 1991. Address for correspondence and reprints: Michael R. Hayden, Department of Medical Genetics, University of British Columbia, The demonstration of linkage between the disease and DNA marker D4S10 (Gusella et al. 1983) has localized the HD gene to the distal end of the short arm of chromosome 4 (Magenis et al. 1986; Wang et al. 1986). In recent years additional markers distal to D4S10 have been isolated which map physically closer to the HD gene (Wasmuth et al. 1988; MacDonald et al. 1989a). ...
The defect causing Huntington disease (HD) has been mapped to 4p16.3, distal to the DNA marker D4S10. Subsequently, additional polymorphic markers closer to the HD gene have been isolated, which has led to the establishment of predictive testing programs for individuals at risk for HD. Approximately 17% of persons presenting to the Canadian collaborative study for predictive testing for HD have not received any modification of risk, in part because of limited informativeness of currently available DNA markers. Therefore, more highly polymorphic DNA markers are needed, which will further increase the accuracy and availability of predictive testing, specifically for families with complex or incomplete pedigree structures. In addition, new markers are urgently needed in order to refine the breakpoints in the few known recombinant HD chromosomes, which could allow a more accurate localization of the HD gene within 4p16.3 and, therefore, accelerate the cloning of the disease gene. In this study we present the identification and characterization of nine new polymorphic DNA markers, including three markers which detect highly informative multiallelic VNTR-like polymorphisms with PIC values of up to .84. These markers have been isolated from a cloned region of DNA which has been previously mapped approximately 1,000 kb from the 4p telomere.
... , Gusella et al. (1983 identified a random DNA fragment, G8, that defines a polymorphic genetic locus (D4S10)-4% recombination from the HD gene. Subsequently, G8 (and, by inference, the HD gene) was localized to the terminal portion of the short arm of chromosome 4 (4p), in band 4p16 ( Gusella et al. 1985;Landegent et al. 1986;Magenis et al. 1986;Wang et al. 1986). At present, there is a need to identify additional markers closer to and, in particular, on the opposite side of the HD gene from G8. Markers on both sides of the HD gene will help make presymptomatic diagnosis of the disease more accurate and will delineate both endpoints of the genomic region containing the disease gene. ...
... As discussed in detail in the Results section, this deletion is indeed interstitial, as determined on the basis of molecular techniques. Gus1654 was established from a patient reported to have a small interstitial deletion that removes the distal portion of 4pl6.1, all of 4pl6.2, and the proximal portion of 4pl6.3 ( Wang et al. 1986). Gus4066 was established from a patient with an unbalanced 4;21 translocation with the breakpoint on 4p originally reported to be within 4pl6.3 (Carpenter et al., in press). ...
... The 622 probe served to verify that a chromosome 4 was present in the majority of the cells from each hybrid. The pKO82 probe enabled us to verify that the chromosome 4 retained was the abnormal one, since previous studies, using either in situ hybridization to metaphase chromosomes ( Magenis et al. 1986;Wang et al. 1986) or quantitative blot hybridization ( Gusella et al. 1985; J. Gusella, personal communication; B. Smith and J. J. Wasmuth, unpublished results) had shown it to be missing from each of the abnormal chromosomes 4 in question. Figure 2 shows autoradiograms of blot hybridizations with 622 ( fig. ...
To facilitate identification of additional DNA markers near and on opposite sides of the Huntington disease (HD) gene, we developed a panel of somatic-cell hybrids that allows accurate subregional mapping of DNA fragments in the distal portion of 4p. By means of the hybrid-cell mapping panel and a library of DNA fragments enriched for sequences from the terminal one-third of the short arm of chromosome 4, 105 DNA fragments were mapped to six different physical regions within 4p15-4pter. Four polymorphic DNA fragments of particular interest were identified, at least three of which are distal to the HD-linked D4S10 (G8) locus, a region of 4p previously devoid of DNA markers. Since the HD gene has also recently been shown to be distal to G8, these newly identified DNA markers are in the direction of the HD gene from G8, and one or more of them may be on the opposite side of HD from G8.
... Little is known concerning the primary genetic defect in this disorder. However, the report of a closely linked polymorphic marker (D4S10) to the gene for HD (Gusella et al. 1983) has allowed preliminary localization of the mutant gene to 4p16 (Magenis et al. 1986;Wang et al. 1986). No evidence for nonallelic heterogeneity has been demonstrated after investigation of more than 50 families of different ancestries . ...
... On the basis of these results, D4S10 can be localized between the telomere and the breakpoint of the chromosome 4 retained in the hybrid in lane 3. This is consistent with the prior mapping assignment of this DNA fragment by in situ hybridization (Magenis et al. 1986;Wang et al. 1986). ...
A polymorphic marker (D4S62) that is genetically closely linked to D4S10 and is in the region of the gene for Huntington disease is described. A four-allele polymorphism is detected when HincII-digested DNA is hybridized with D4S62. D4S62 maps, by Southern blot analysis using somatic-cell hybrids, to 4p16.1 closer to the centromere than does D4S10. The use of the polymorphisms detected by D4S62 increases the informativeness of markers close to the gene for Huntington disease and will be useful for preclinical diagnosis. D4S62 detects transcripts of approximately 6,000 nucleotides in rat, mouse, and monkey liver and brain. This represents the first demonstration of conserved expressed sequences close to the gene for Huntington disease.
In Britain, about 14 000 infants each year are born with a genetic disorder. The area covered by the Northern Regional Health Authority has a population of 3.1 million and 40 000 annual live births of which 1200 are genetically abnormal. However, there are about 60 000 people in the region who are known carriers of single gene defects and a very much larger number who are at risk of being carriers. Such genetically determined diseases cause chronic disability, and often the fear of early death and handicap leads to unnecessary abortion of normal fetuses, lifelong anxiety and childlessness. Molecular genetic techniques are advancing at a rapid rate and now offer hope to many people by demonstrating that they are not carriers of a particular defective gene or that their fetus is normal. In the minority of cases where a fetal abnormality which will cause chronic illness, either in childhood or in later life, is detected, early selective abortion can be offered.
Huntington's disease (HD) is tightly linked to genetic markers in 4p16.3. We have used a regional somatic cell hybrid mapping panel to isolate and map 25 cosmids to the proximal portion of 4p16.3 and 17 cosmids to the distal portion. The latter were positioned by long-range restriction mapping relative to previously mapped markers. One cosmid, L6 (D4S166), spans the critical breakpoint in the mapping panel that distinguishes proximal and distal 4p16.3. Four of the cosmids mapped distal toD4S90, the previous terminal marker on 4p, and stretched to within 75 kb of the telomere. Several of the cosmids that mapped between L6 andD4S90 were clustered near a number of previously isolated clones in a region with many NotI sites. Cosmid E4 (D4S168) was localized immediately proximal to the one remaining gap in the long-range restriction map of distal 4p16.3. Although pulsed field gel mapping with E4 failed to link the two segments of the map, the intervening gap was excluded as a potential site for theHD gene by genetic analysis.
Interstitial deletion of the proximal short arm of chromosome 4 has rarely been described. This defect is associated with variable clinical manifestations, including mental retardation, unusual facial appearance, and minor limb abnormalities. We describe a girl diagnosed with moderate mental retardation and seizures with an interstitial deletion of the short arm of chromosome 4 [46, XX, del(4)(p12p15.2)].
To identify expressed sequences within candidate regions for the Huntington's disease (HD) gene in 4p16.3, we isolated the gene encoding the beta subunit of the human cGMP phosphodiesterase (PDEB). We formally assessed this as a candidate gene for HD based on it's expression in brain, the demonstration of linkage disequilibrium between intragenic DNA markers and HD, and the demonstration that mice with a mutation in this gene have a reduction of neurons in particular brain regions. We investigated all 22 exons of PDEB and 5'-flanking region for point mutations in 16 HD patients of different ethnic origins using single strand conformational polymorphism analysis. The underlying DNA changes found initially exclusively in HD patients were excluded as the cause for HD.
Traditionally, a clinical diagnosis of Huntington disease (HD) presents no problems in patients with a positive family history, consistent with autosomal dominant inheritance, chorea or other extrapyramidal motor signs, and progressive mental decline (1). However, due to the slowly progressive nature of the disease and the slow evolution of signs and symptoms, it is often difficult to determine when at risk individuals are showing early signs. Moreover, the clinical recognition of both early and late-onset cases, and of choreic patients in whom a family history is lacking, presents special diagnostic challenges.
In recent years, much progress has been made in the recognition of early clinical signs of the disease. Factors which have contributed to this understanding include the longitudinal study of large cohorts of at-risk individuals, particularly in Venezuela, the data from predictive testing programs, and the application of positron emission tomography (PET)-scanning to individuals without overt chorea. We are now able to identify persons at risk as being affected before they display overt and obvious involuntary movements.
