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PubMed2000

A human model for multigenic inheritance: phenotypic expression in Hirschsprung disease requires both the RET gene and a new 9q31 locus.

Reduced penetrance in genetic disorders may be either dependent or independent of the genetic background of gene carriers. Hirschsprung disease (HSCR) demonstrates a complex pattern of inheritance with approximately 50% of familial cases being heterozygous for mutations in the receptor tyrosine kinase RET. Even when identified, the penetrance of RET mutations is only 50-70%, gender-dependent, and varies with the extent of aganglionosis. We searched for additional susceptibility genes which, in conjunction with RET, lead to phenotypic expression by studying 12 multiplex HSCR families. Haplotype analysis and extensive mutation screening demonstrated three types of families: six families harboring severe RET mutations (group I); and the six remaining families, five of which are RET-linked families with no sequence alterations and one RET-unlinked family (group II). Although the presence of RET mutations in group I families is sufficient to explain HSCR inheritance, a genome scan reveals a new susceptibility locus on 9q31 exclusively in group II families. As such, the gene at 9q31 is a modifier of HSCR penetrance. These observations imply that identification of new susceptibility factors in a complex disease may depend on classification of families by mutational type at known susceptibility genes.

Chromosomes, Human, Pair 9↗
PubMed2001

Audiologic aspects of the search for DFNA20: a gene causing late-onset, progressive, sensorineural hearing loss.

OBJECTIVE: The purpose of this research was to identify the gene responsible for a novel form of nonsyndromic, late-onset, bilateral, progressive, sensorineural hearing loss in a Michigan family of English descent. This report describes the audiologic aspects of the search. DESIGN: Fifty-eight members of the family served as subjects for the study. Family pedigree information was gathered from family interviews, family records, birth and death registration records and census data. Audiologic evaluation was used to describe the hearing loss (phenotype) and classify family members as affected or unaffected based on hearing status. These data then were used in a linkage analysis, a process in which the inheritance of a trait is compared with the inheritance of genetic markers and statistically significant associations are sought. RESULTS: The team mapped the hearing loss to the long arm of chromosome 17 at band 17q25. The pattern of inheritance is autosomal dominant. The search for the gene is continuing using a candidate gene approach. CONCLUSIONS: The hearing loss demonstrated by this mid-Michigan family is a novel form of nonsyndromic, genetic, late-onset, bilateral, progressive, sensorineural hearing loss. The locus of the gene, the 20th for autosomal dominant hearing loss, is at band 17q25 of chromosome 17.

Adolescent↗
PubMed1980

Autosomal recessive inheritance of atrichia congenita.

Two families, each with two sibs presenting atrichia congenita, were studied. Histopathological studies of scalp biopsies from affected revealed absence of hair follicles. The pedigree data were interpreted as corroborative of a previously postulated autosomal recessive pattern of inheritance.

Alopecia↗
PubMed1995

Charcot-Marie-Tooth disease: molecular characterization of patients from central and southern Italy.

The syndrome of peroneal muscular atrophy, or Charcot-Marie-Tooth (CMT), disease represents the most common inherited peripheral neuropathy, with a prevalence of about 1 per 2500. The disease is usually transmitted in an autosomal dominant fashion, although it can display all the mendelian patterns of inheritance. The chromosome 17-linked form (CMT1a) appears to be the most common form of the disease in all the ethnic groups studied so far, Italians included, and is due to a tandem duplication in 17p11.2. In order to study the distribution of CMT types and to establish a genotype-phenotype correlation in patients from Central and Southern Italy, we collected 19 CMT pedigrees diagnosed in the years 1992-1993. Simple tandem repeats (STR) polymorphism analysis with the marker RM11-GT and Southern blotting with the probes pVAW409R3 and pVAW412 were performed, demonstrating a high prevalence (about 60%) of 17p duplication in the families studied. No clinical or electrophysiological differences were noted between CMT1 patients with or without 17p duplication, respectively. Two families affected by CMT2 showed no evidence of rearrangement at the D17S122 locus. These data are consistent with the hypothesis of a different molecular basis for CMT2.

Blotting, Southern↗
PubMedDate not supplied

Hereditary cancer and its clinical implications: a view.

In hereditary cancers the responsible inherited cancer genes are defective (mutated) anti-oncogenes (tumour suppressor genes). This inherited mutation is present in all cells of the organism, and only leads to cancer if in a somatic cell a complete set of specific cancer mutations is accumulated. Since one defective anti-oncogene has been inherited, only three additional somatic cancer mutations are required, according to our previously published view (Anticancer Res 10:1990). The number of de novo arising tumour cells in such a person is thus multiplied by a factor equal to the reverse of the mutant frequency, that is about 10(4)-10(5). This can be observed e.g. in retinoblastoma. Mutations occur in proliferating cells only. Consequently cancer mutations also depend on cell proliferation. If an inherited cancer mutation predisposes to cancer formation in certain organs, then the cancer risk in these organs is enhanced by 10(4)-10(5) times. Tumours in these organs will appear simultaneously if the number of cells and the growth kinetics are similar. This is of course observed in paired organs, like the retina and the female breast. In cancer family syndromes different organs may be affected at the same time. Examples are type I and type II cancer family syndrome and multiple endocrine neoplasia type 1 2a, and 2b. The secondly diagnosed tumours are not caused by metastatic spread. Tumours in two organs will arise at difference times if the number of end cells per organ and the growth kinetics differ. In this case the second tumour is called a second primary malignancy and is not caused by metastatic spread. A good example are the second primary malignancies in hereditary retinoblastoma. The inherited defective anti-oncogene is a recessive gene. This defective inherited gene causes a 10(4)-10(5) fold increase of the normal tumour incidence. This means that nearly always one or more tumours will arise. Evidently, this pattern of inheritance has led to the erroneous conclusion that the genetic abnormality is dominant at the level of the chromosome. The 10(4)-10(5) times enhanced tumour incidence in hereditary cancer is helpful for the clinical recognition of hereditary cancer. That is, hereditary cancer can be recognized not only by family history, but also by early occurrence, the multifocal and bilateral localisation, its occurrence as cancer family syndrome or by second primary malignancies. It is thus recommended to screen patients and families with hereditary cancer for first and second primary tumours. Treatment of patients with hereditary tumours requires extra care to avoid additional cancer mutations.(ABSTRACT TRUNCATED AT 400 WORDS)

Genes, Dominant↗
PubMedDate not supplied

A novel mutation in the short-wavelength-sensitive cone pigment gene associated with a tritan color vision defect.

Inherited tritan color vision deficiency is caused by defects in the function of the short-wavelength-sensitive (S) cones. This heterozygous group of disorders has an autosomal dominant pattern of inheritance. Amino acid variations of the S cone opsin are rare and all that have been identified thus far are associated with inherited tritan color vision defects. Here we report the identification of a 30-year-old male who made errors on standard color vision tests consistent with the presence of a mild tritan color vision deficiency. We tested the hypothesis that his color vision impairment was due to a mutation in the S cone photopigment gene. He was found to be heterozygous for a mutation that caused the amino acid proline to be substituted in place of a highly conserved leucine at amino acid position 56 in the S cone opsin. This mutation was absent in 564 S cone photopigment genes from 282 subjects who did not make tritan errors. Thus, we conclude that this mutation disrupts the normal function of S cones.

Adult↗
PubMed2006

A novel locus for X-linked retinitis pigmentosa.

INTRODUCTION: Retinitis pigmentosa (RP) is the most prevalent group of inherited retinopathies and demonstrates considerable clinical and genetic heterogeneity, with wide variations in disease severity, progression, and gene involvement. We studied a large family with RP to determine the pattern of inheritance and to identify the disease-causing gene/locus. MATERIALS AND METHODS: Ophthalmic examination was performed on 35 family members to identify affected individuals and carriers and to characterise the disease phenotype. Genetic linkage analysis was performed using short tandem repeat (STR) polymorphic markers encompassing the known loci for Xlinked RP (xlRP) including RP2, RP3, RP6, RP23, and RP24. Mutation screening was performed by direct sequencing of PCR-amplified genomic DNA of the RP2 and RPGR genes of the affected individuals. RESULTS: A highly penetrant, X-linked form of RP was observed in this family. Age of onset was from 5 to 8 years and visual acuity ranged from 20/25 in children to light perception in older adults. Linkage analysis and direct sequencing showed that no known loci/genes were associated with the phenotype in this kindred. CONCLUSION: A novel disease gene locus/loci is responsible for the xlRP phenotype in this family.

Adolescent↗
PubMed1977

Peptic ulcer disease--a heterogeneous group of disorders?

The familial aggregation of peptic ulcer disease has been well established, as has its association with such clear-cut genetic factors as blood group O and nonsecretor status. However, the genetics of this disorder, or group of disorders, is still in question. Polygenic inheritance is the prevailing hypothesis that has been proposed for peptic ulcer. This hypothesis was based primarily on the exclusion of a simple mode of inheritance for all ulcer disease. Genetic heterogeneity is an alternative hypothesis that can explain both the familial aggregation of peptic ulcer disease and the lack of a simple Mendelian pattern of inheritance. The evidence for genetic heterogeneity in peptic ulcer disease is reviewed, and studies are proposed to test this hypothesis.

ABO Blood-Group System↗
PubMed1992

Cowden's disease. A case report with analyses at the molecular level.

Cowden's disease (multiple hamartoma syndrome) is characterized by multiple hamartomas of ectodermal, endodermal, and mesodermal origin, a high incidence of malignant tumors of the breast and/or thyroid gland, and an autosomal dominant pattern of inheritance. Similar to sporadic breast cancer, chromosomal studies have not elucidated the cause of this syndrome. The authors report the case of a patient with this syndrome and analyze the pattern of amplification or rearrangement of three genes: the HER-2/neu oncogene, the ras oncogene, and the estrogen-inducible gene, pS-2. All three of these genes were present in single copies without translocations. It was noteworthy that three of the most important genes currently studied in relation to breast cancer existed in a unamplified unrearranged state in this patient. Those with clinical manifestations of Cowden's disease may be candidates for prophylactic bilateral total mastectomy, and the authors recommend that these patients undergo this procedure by their third decade of life. An alternative to this approach would entail monthly self examinations, breast examinations by the patient's physician every 3 months, bilateral mammograms every 6 to 12 months, and biopsy of any suspicious lesions. It is crucial, however, that these patients be identified by their mucocutaneous lesions and family history before an underlying malignant lesion develops.

Adult↗
PubMed1995

Absence of linkage of apparently single gene mediated ADHD with the human syntenic region of the mouse mutant Coloboma.

Attention deficit disorder (ADHD) is a complex biobehavioral phenotype which affects up to 8% of the general population and often impairs social, academic, and job performance. Its origins are heterogeneous, but a significant genetic component is suggested by family and twin studies. The murine strain, coloboma, displays a spontaneously hyperactive phenotype that is responsive to dextroamphetamine and has been proposed as a genetic model for ADHD. Coloboma is a semi-dominant mutation that is caused by a hemizygous deletion of the SNAP-25 and other genes on mouse chromosome 2q. To test the possibility that the human homolog of the mouse coloboma gene(s) could be responsible for ADHD, we have carried out linkage studies with polymorphic markers in the region syntenic to coloboma (20p11-p12). Five families in which the pattern of inheritance of ADHD appears to be autosomal dominant were studied. Segregation analysis of the traits studied suggested that the best fitting model was a sex-influenced, single gene, Mendelian pattern. Several genetic models were evaluated based on estimates of penetrance, phenocopy rate, and allele frequency derived from our patient population and those of other investigators. No significant linkage was detected between the disease locus and markers spanning this chromosome 20 interval.

Adolescent↗
PubMed1991

Nonsyndromal profound genetic deafness in childhood.

About one-half of children with profound deafness have an autosomal recessive or autosomal dominant inherited type of deafness. The X-linked inherited types of deafness are rare. About one out of three profoundly deaf children has an autosomal recessive form of inherited deafness. At sometime during their life a syndromal diagnosis can be made in one out of four cases with an autosomal recessive form of deafness. Therefore in about 25% of all the children with profound deafness, a nonsyndromal autosomal recessive type of genetic deafness will be involved. It is still not clear how many different genes are responsible for this. The more severe the deafness in a child, the greater the chance that an autosomal recessive etiology is involved. The autosomal dominant inherited types of deafness are significantly more frequent in cases where the hearing loss in the best ear is less than 80-90 db. About one-half of the autosomal dominant inherited cases show a classical syndromal type of deafness based on clinical features. In the other half, some audiometrically recognizable types of deafness can be diagnosed after an autosomal dominant pattern of inheritance has been established. Additional genetic knowledge based on gene-linkage studies is needed to provide better tools for the more accurate diagnosis of genetic etiology in a profoundly deaf child. Adequate pedigrees are quite rare and such pedigrees are expected to become even more scarce as a result of a diminishing ratio of consanguineous marriages. It is necessary to start gene-linkage studies in these existing pedigrees to trace the genes responsible for this nonsyndromal type of profound genetic deafness in childhood.

Child↗
PubMed1999

Familial dilated cardiomyopathy: evidence for genetic and phenotypic heterogeneity. Heart Muscle Disease Study Group.

OBJECTIVES: This study was performed to evaluate the characteristics, mode of inheritance and etiology of familial dilated cardiomyopathy (FDC). BACKGROUND: A genetic form of disease transmission has been identified in a relevant proportion of patients with dilated cardiomyopathy (DCM). Variable clinical characteristics and patterns of inheritance, and an increased frequency of cardiac antibodies have been reported. An analysis of FDC may improve the understanding of the disease and the management of patients. METHODS: Of 350 consecutive patients with idiopathic DCM, 281 relatives from 60 families were examined. Family studies included clinical examination, electrocardiography, echocardiography and blood sampling. Of the 60 DCM index patients examined, 39 were attributable to FDC and 21 were due to sporadic DCM. Clinical features, histology, mode of inheritance and autoimmune serology were examined, molecular genetic studies were undertaken and the difference between familial and sporadic forms was analyzed. RESULTS: Only a younger age (p = 0.0005) and a higher ejection fraction (p = 0.03) could clinically distinguish FDC patients from those with sporadic DCM. However, a number of distinct subtypes of FDC were identified: 1) autosomal dominant, the most frequent form (56%); 2) autosomal recessive (16%), characterized by worse prognosis; 3) X-linked FDC (10%), with different mutations of the dystrophin gene; 4) a novel form of autosomal dominant DCM with subclinical skeletal muscle disease (7.7%); 5) FDC with conduction defects (2.6%), and 6) rare unclassifiable forms (7.7%). The forms with skeletal muscle involvement were characterized by a restrictive filling pattern; the forms with isolated cardiomyopathy had an increased frequency of organ-specific cardiac autoantibodies. Histologic signs of myocarditis were frequent and nonspecific. CONCLUSIONS: Familial dilated cardiomyopathy is frequent, cannot be predicted on a clinical or morphologic basis and requires family screening for identification. The phenotypic heterogeneity, different patterns of transmission, different frequencies of cardiac autoantibodies and the initial molecular genetic data indicate that multiple genes and pathogenetic mechanisms can lead to FDC.

Adolescent↗
PubMed1991

Familial gastric polyposis revisited. Autosomal dominant inheritance confirmed.

We update and review a large pedigree originally described by Santos and Magalhães with familial gastric polyposis and a high incidence of gastric cancer. The present observation of male-to-male transmission of the disease clearly demonstrates the autosomal dominant pattern of inheritance. The histologic review of the polyps present in several members of the family allowed the diagnosis of hyperplastic polyposis. Eight members of the family (two with concomitant gastric pathology) have severe cutaneous psoriasis. This finding may represent the existence of two different disorders segregating in the family or, alternatively, pleiotropic manifestations of the same gene.

Adenocarcinoma, Mucinous↗
PubMed1989

Inherited disorders associated with colorectal cancer.

There is an increased risk of colorectal cancer among first degree relatives of affected men and women which is greater among relatives of young index patients. The high risk in some families can be explained by Mendelian patterns of inheritance and some syndromes associated with colorectal cancer have been recognized. Syndrome recognition with an accurate knowledge of the natural history of diseases caused by a single gene effect can offer opportunities for exploration of some of the mechanisms of carcinogenesis as well as enable more accurate predictions of diagnosis in susceptible individuals and in pregnancy. Recent progress with familial adenomatous polyposis illustrates some of the opportunities for prevention of colorectal cancer which may arise with syndrome recognition in the future.

Adenoma↗
PubMed2004

GJB2 mutations in patients with non-syndromic hearing loss from Northeastern Hungary.

Mutations in the GJB2 gene encoding the gap-junction protein connexin 26 have been identified in many patients with childhood hearing impairment (HI). One single mutation, c.35delG, accounts for the majority of mutations in Caucasian patients with HI. In the present study we screened 500 healthy control individuals and a group of patients with HI from Northeastern Hungary for GJB2 mutations. The patients' group consisted of 102 familial from 28 families and 92 non-familial cases. The most common mutation in the Hungarian population is the c.35delG, followed by the c.71G>A (p.W24X) mutation. 34.3% of the patients in the familial group were homozygous, and 17.6% heterozygous for 35delG. In the non-familial group the respective values were 37% and 18% (allele frequency: 46.2%). In the general population an allele frequency of 2.4% was determined. Several patients were identified with additional, already described or new GJB2 mutations, mostly in heterozygous state. The mutation c.380G>A (p.R127H) was formerly found only in heterozygous state and its disease relation was controversial. We demonstrated the presence of this mutation in a family with three homozygous patients and 4 heterozygous unaffected family members, a clear indication of recessively inherited HI. Furthermore, we provided evidence for the pathogenic role of two new mutations, c.51C>A (p.S17Y) and c.177G>T (p.G59V), detected in the present study. In the latter case the pattern of inheritance might be dominant. Our results confirm the importance of GJB2 mutations in the Hungarian population displaying mutation frequencies that are comparable with those in the Mediterranean area.

Adolescent↗
PubMed1992

Monosomy 7 myeloproliferative disease in children with neurofibromatosis, type 1: epidemiology and molecular analysis.

Loss of constitutional heterozygosity is a common molecular feature of cancers in which inactivation of one or more tumor suppressor genes is thought to contribute to tumorigenesis. Recent evidence suggests that the gene responsible for neurofibromatosis, type 1 (NF-1), belongs to this class of heritable cancer genes. Children with NF-1 show an increased incidence of myeloid leukemia, including juvenile chronic myelogenous leukemia (JCML) and, perhaps, the myeloproliferative syndrome (MPS) associated with bone marrow monosomy 7 (Mo 7). We have investigated five children with Mo 7: three with NF-1 and two others with suggestive evidence of NF-1. Southern blotting experiments performed in four patients showed no loss of heterozygosity in bone marrow specimens using probes linked to the NF-1 locus on the long arm of chromosome 17. Both of our patients with familial NF-1 inherited the disease from their mothers, as did 14 of 19 other cases of myeloid leukemia in children with familial NF-1. Seventeen of these 21 children were boys. Myeloid leukemia developed in 12 boys and four girls who inherited NF-1 from their mothers, and in five boys who inherited the disease from their fathers. Father-to-daughter transmission was not observed. Taken together, the presence of chromosome 7 deletions in the leukemias of children with NF-1, a pattern of inheritance favoring maternal transmission of NF-1, and the marked predilection for boys to develop JCML and Mo 7 suggest a multistep mechanism of oncogenesis in which epigenetic factors might play a role. Further investigation is required to determine if the NF-1 genes in the leukemic bone marrows of these patients have acquired point mutations or small deletions.

Blotting, Southern↗
PubMed2003

Characterization of the neoplastic phenotype in the familial atypical multiple-mole melanoma-pancreatic carcinoma syndrome.

BACKGROUND: Previous studies suggest that the familial atypical multiple-mole melanoma (FAMMM) syndrome may predispose affected families to nonmelanoma carcinomas, including adenocarcinoma of the pancreas. It has been found that many of these families harbor mutations in the CDKN2A gene on chromosome 9p21. The phenotypic expression of CDKN2A mutations in these families has not been characterized fully. METHODS: The authors studied eight families that appeared to inherit multiple nevi, cutaneous melanomas, and pancreatic carcinomas in association with a CDKN2A germline mutation. The expression of disease within these families was examined, and segregation ratios were estimated to assess the patterns of inheritance according to various definitions of phenotype. RESULTS: Either multiple nevi or pancreatic carcinoma was diagnosed in 53% of first-degree relatives of the probands. The offspring of parents affected with multiple nevi, melanoma, or pancreatic carcinoma were significantly more likely to be affected themselves compared with the offspring of unaffected parents (48.9% vs. 16.7%; P = 0.004). CONCLUSIONS: The current results provide additional evidence that multiple nevi, melanoma, or pancreatic carcinoma may be inherited as autosomal-dominant traits in families known to harbor CDKN2A mutations. Other malignancies may be a part of the phenotype in these families, although this hypothesis requires additional study.

Adult↗