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Results for “Genotype-phenotype”

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PubMed1991

Single-strand conformation polymorphism for detection of mutations and base substitutions in phenylketonuria.

In the past few years, more than 20 different mutations have been reported in hyperphenylalaninemias. In southwestern Europe and Mediterranean countries, however, the mutant genotypes reported account for only a fraction (27%) of all mutant alleles at the phenylalanine hydroxylase (PAH) locus, and most of the mutations causing the disease remain unknown. In order to develop a strategy for rapid detection of mutation-containing exons, we applied the single-strand conformation-polymorphism (SSCP) technique to exons 3, 5, 7, and 12 of the PAH gene. We observed five abnormal patterns of migration in mutant PAH genes, and we consistently found base substitutions in the corresponding exons, with no false-positive results. By this procedure, two novel putative mutations were detected in the seventh exon of the PAH gene, (A259V and Y277D) and we were able to demonstrate that the delta I94, R158Q, R408W, and E280K mutations were easily detectable by the SSCP technique. This procedure is therefore of particular interest for rapid detection of mutation-containing exons and for determination of further genotype-phenotype correlations in hyperphenylalaninemias.

Base Sequence↗

PubMed1983

A family with segregating triplicated alpha globin loci and beta thalassemia.

In this article we report a Sardinian family, in which a beta-thalassemia gene and a triple alpha-globin loci, counterpart of the rightward deletion type alpha-thalassemia-2, were segregating. The analysis of the genotype-phenotype correlations in the different family members allowed us to give an outline of the manifestations associated with different genotype combinations. The heterozygote for the triple alpha-loci showed no consistent abnormal clinical or hematologic characteristics and presented balanced alpha/beta-globin chain synthesis. In the homozygous state for this lesion, the only phenotypic expression was a slightly imbalanced globin chain synthesis. The combination of heterozygous beta-thalassemia with the heterozygous state for the triple alpha-globin loci produced no clinical manifestations and showed a hematologic phenotype indistinguishable from that of heterozygous beta-thalassemia. On the other hand, the combination of the homozygous state for the triple alpha-globin gene loci and the heterozygous state for beta-thalassemia produced a clinical picture of thalassemia intermedia with a very mild clinical course, minor increase of fetal hemoglobin (HbF) levels, and a pronounced imbalance of globin chain synthesis.

Adult↗

PubMed1982

Small accessory chromosomes (SAC) and their genotype--phenotype correlation.

A total of 39 carriers of small accessory chromosomes (SAC) was found among 32,930 patients karyotyped in Division of Human Genetics, Catholic University, Leuven, Belgium, in the years 1966-1981. In majority of SAC carriers the origin of extra-chromosome material remained unknown (21 out of 29 index patients), even when applying different banding techniques. The only common feature of all described SAC seems to be the presence of C-banded heterochromatin. The genotype-phenotype correlation in SAC carriers has been discussed.

Adolescent↗

PubMed1994

Neurofibromatosis type 1.

The authors review the present data on the clinical and molecular aspects of neurofibromatosis type 1 (NF1). In the clinical part attention is given to the frequent observation of learning disabilities in NF1 children. In these children visual-spatial integration deficits and an increased incidence of school performance problems are observed. The NF1 gene is located on chromosome 17 (17q11.2), and is highly conserved across species. Up to now only a limited number of mutations in this gene have been characterized, and this shows a general lack of genotype-phenotype correlation. Evidence is given that the NF1 gene acts as a true tumor suppressor gene and that oncogenesis in NF1 is a complex multistep phenomenon with the second hit in the NF1 gene as the initiating event. The importance of specialized multidisciplinary outpatient clinics for neurofibromatosis is emphasized because of the complexity of follow-up and treatment of these patients.

Child↗

PubMed1993

Molecular cytogenetics: solid tumors and leukemia.

Acute leukemia represents one of the best-studied malignancies. Consequently, numerous dogmas have evolved over the years. One dogma to which we subscribe is that leukemia is a genetic disease and that the behavior of leukemic cells and their response to therapy is determined largely by their genetic characteristics. The relative ease of metaphase generation and culture of single leukemic cells, well-defined morphologic criteria, and availability of phenotyping reagents has contributed to a wealth of information about the karyotypic, genetic, and functional properties of these cells. Nevertheless, establishment of genotype-phenotype relationships has been particularly elusive. The genetic evolution of leukemias and the consequences of specific aberrations remains to be determined. We describe the power of new molecular cytogenetic tools, fluorescence in situ hybridization, and comparative genomic hybridization to measure the genetic evolution of leukemic cells. Lessons learned from application of these techniques to solid tumors and speculations about similar approaches to analysis of leukemia are addressed.

Cytogenetics↗

PubMed1993

[Familial form of partial androgen insensitivity (Reifenstein syndrome): arginine-histidine mutation in position 840 in the androgen receptor].

In a large kindred with Reifenstein syndrome, we performed the molecular analysis of the androgen receptor gene. Since the biochemical characteristics of the androgen receptor, determined on the cultured genital skin fibroblasts, showed a drastic decrease of the androgen binding capacity, we assumed that a point mutation was located in exons 4-8 encoding the carboxy-terminal domain of the receptor. Enzymatic amplifications of these exons did not point out any deletions. Direct sequencing showed a G-A point mutation at position 2818 of exon 7 responsible for an arginine-histidine substitution at position 840 of the androgen receptor. The presence of the same mutation has been reported by other groups in four unrelated patients. Its association with different phenotypes of androgen insensitivity and different biochemical characteristics of the androgen receptor pointed out the complexity of the genotype-phenotype relationship in androgen insensitivity. Moreover the identification of the point mutation gave us the opportunity to perform a prenatal exclusion diagnosis of Reifenstein syndrome in this high-risk family.

Arginine↗

PubMed1994

[Genetic heterogeneity of retinitis pigmentosa].

The authors present a classification of retinitis pigmentosa (rp) based on the modes of inheritance. Known genetic conditions of autosomal recessive, X-linked recessive and autosomal dominant forms of rp are shown, presenting molecular principles of the illness. They also describe clinical subtypes of rp with suggested genotype-phenotype correlations and principles of modern genetic diagnostics and genetic counselling.

Female↗

PubMed1994

DNA polymorphisms and conditions for SSCP analysis of the 20 exons of the ret proto-oncogene.

Recently identified mutations affecting different domains of the RET proto-oncogene are associated with Multiple Endocrine Neoplasia type 2A (MEN 2A) and type 2B (MEN 2B), familial and sporadic Medullary Thyroid Carcinomas (MTC) and Hirschsprung disease (HSCR). In order to facilitate the screening for RET mutations, and to study possible genotype-phenotype correlations, we established exon-intron junctions and extended the intronic sequences flanking the 20 exons of this gene. This made it possible to design primers and to develop PCR conditions useful for SSCP analysis of the whole RET coding sequence. Nine conformational variants were observed which after sequencing turned out to be 8 silent mutations and a conservative amino acid substitution. Restriction analysis performed on DNA samples from unrelated controls confirmed the polymorphic nature of six of these nucleotide changes and made it possible to estimate the frequency of the corresponding alleles.

Base Sequence↗

PubMed1993

[Molecular genetic study of cystic fibrosis in the Chilean population. Relationship to its clinical expression].

Aiming to establish a genotype-phenotype relationship and to search a clinical expression in heterozygotes, 25 Chilean subjects with Cystic Fibrosis and 165 relatives were subjected to a clinical-molecular study. The most common mutations found worldwide were studied: delta F-508, G-542X, N-1303K, R-553X and G551D. Clinical and laboratory assessment comprised chest X-rays, spirometry, clinical evaluation, nutritional assessment, sweat test and carotenemia. Age at diagnosis was lower among homozygotes for the mutation delta F-508. In this group, Brasfield and Schawchman scores were better, probably due to an earlier initiation of treatment. No other differences were found among genotypic groups or relatives. Genetic markers indicated a higher european component of the sample, compared to the general Chilean population.

Adolescent↗

PubMed1994

Impact of molecular genetics in cardiac diseases.

Genetic linkage mapping has become an important technology applied to the study of human biology and in particular, for the delineation of the molecular basis of diseases through gene isolation and characterization of mutations in DNA. This approach was applied to cardiac hereditary disorders only a few years ago through the analysis of familial hypertrophic cardiomyopathy and congenital long QT syndrome. For both diseases, there is a striking genetic heterogeneity and analyses of genotype-phenotype correlations are underway. Familial occurrence is likely to play also an important role in idiopathic dilated cardiomyopathy. Genetic testing and risk stratification will be more complicated than it was initially expected, but hope is now there to discover new ways for preventing, diagnosing and treating deadly cardiac disorders.

Cardiomyopathy, Dilated↗

PubMed1995

[Familial polyposis coli].

Familial polyposis coli (FAP) presents multiple adenomas in the large bowel. Also, polyps in the upper gastrointestinal tract are observed in some cases of FAP. Since the risk of developing colorectal cancer is almost 100% in FAP, patients need surgical treatment (colectomy) after a diagnosis of FAP is made. After a gene for FAP (APC gene) was identified, an accurate diagnosis of FAP is becoming possible by examining APC gene, even though patients show no clinical manifestations. Many studies revealed various mutations of APC gene and examined the relation between the site of the germline APC mutation and the phenotypic expression of FAP. These studies suggested that there was a Genotype-Phenotype Correlation in FAP. Some differences of clinical features in FAP, such as profuse type and attenuated type of FAP (AAPC), are now considered to be caused by the difference of the site of the germline APC mutation.

Adenomatous Polyposis Coli↗

PubMed1996

Molecular definition of red cell Rh haplotypes by tightly linked SphI RFLPs.

The Rh blood group system of human red cells contains five major antigens D, C/c, and E/e (the latter four designated "non-D") that are specified by eight gene complexes known as Rh haplotypes. In this paper, we report on the mapping of RH locus and identification of a set of SphI RFLPs that are tightly linked with the Rh structural genes. Using exon-specific probes, we have localized the SphI cleavage sites resulting in these DNA markers and derived a comprehensive map for the RH locus. It was found that the SphI fragments encompassing exons 4-7 of the Rh genes occur in four banding patterns or frameworks that correspond to the distribution and segregation of the common Rh haplotypes. This linkage disequilibrium allowed a genotype-phenotype correlation and direct determination of Rh zygosity related to the Rh-positive or Rh-negative status (D/D, D/d, and d/d). Studies on the occurrence of SphI RFLPs in a number of rare Rh variants indicated that Rh phenotypic diversity has taken place on different haplotype backgrounds and has arisen by diverse genetic mechanisms. The molecular definition of Rh haplotypes by SphI RFLP frameworks should provide a useful procedure for genetic counseling and prenatal assessment of Rh alloimmunization.

Base Sequence↗

PubMed1996

Germ line mutation at BRCA1 affects the histoprognostic grade in hereditary breast cancer.

Histoprognostic grade is a determinant parameter to select the initial therapeutic strategy in breast cancer. Our aim was to analyze the grade repartition in BRCA1-associated breast cancer (BC) and to explore the possible connections between grade and the BRCA1 gene function. We first compared 27 BRCA1-associated BCs from 14 families with 4,461 cases from an administrative district registry and 242 cases from a hospital-based registry, matching for grade and constitutive elements, and then considered their repartition in families. We observed a prevalence of grade 3 (P < 0.0001) in BRCA1-associated BC. This was attributed mainly to nuclear polymorphism (P < 0.0001), mitotic activity (P < 0.0001), and tubular differentiation (P = 0.0004), implying that BRCA1-associated BCs are highly proliferating tumors. Moreover, it is suggested that grade segregates as a genetic trait within families (P = 0.0015), and this was attributed to the mitotic index segregation only (P = 0.0005). Therefore grade, through its components, could be interpreted as the morphological translation of the BRCA1 germ line mutation. Thus, a genotype-phenotype correlation may exist between the type of mutation and the aggressiveness of the disease. These findings are bound to have an important impact in the care management of hereditary breast cancer at the individual and at the familial level and in the comprehensive approach of breast cancer development.

Adult↗

PubMed1995

[A study evaluating the correlation between the phenotype and genotype among 65 cystic fibrosis patients].

Among 65 CF diagnosed patients with both CFTR gene mutations known genotype-phenotype studies were performed. Correlation between pancreatic insufficiency and so called "severe mutations" was found. Respiratory tract symptoms do not seem to depend on one specific mutation as well as meconium ileus is not only limited to the group of patients with delta F508/delta F508 genotype. Some other genotype - clinical features correlation in CF patients are discussed.

Adolescent↗

PubMedDate not supplied

[Mutation analysis in Hunter patients].

Mutations of the iduronate-2-sulfatase gene have been identified as responsible of Hunter syndrome or mucopolysaccharidosis type II. About 20% of the patients have deletions of the whole gene or other major structural alterations. The mutations found so far include: 34 missense, 8 nonsense, 11 small deletions from 1 to 3 bp, 2 deletions of 8 pb, 2 insertions of 1 bp and 2 insertions of 14 bp, with most leading to a frameshift and premature chain termination. Also 8 different splice-site mutations leading to insertions or deletions in the mRNA have been tabulated. Knowledge of the primary genetic defect allows insight into genotype-phenotype correlation and allows a better understanding of the structure and function of iduronate-2-sulfatase.

Base Sequence↗

PubMed1996

Germ-line mutations in the neurofibromatosis 2 gene: correlations with disease severity and retinal abnormalities.

Neurofibromatosis 2 (NF2) features bilateral vestibular schwannomas, other benign neural tumors, and cataracts. Patients in some families develop many tumors at an early age and have rapid clinical progression, whereas in other families, patients may not have symptoms until much later and vestibular schwannomas may be the only tumors. The NF2 gene has been cloned from chromosome 22q; most identified germ-line mutations result in a truncated protein and severe NF2. To look for additional mutations and clinical correlations, we used SSCP analysis to screen DNA from 32 unrelated patients. We identified 20 different mutations in 21 patients (66%): 10 nonsense mutations, 2 frameshifts, 7 splice-site mutations, and 1 large in-frame deletion. Clinical information on 47 patients from the 21 families included ages at onset and at diagnosis, numbers of meningiomas, spinal and skin tumors, and presence of cataracts and retinal abnormalities. We compared clinical findings in patients with nonsense or frameshift mutations to those with splice-site mutations. When each patient was considered as an independent random event, the two groups differed (P < or = .05) for nearly every variable. Patients with nonsense or frameshift mutations were younger at onset and at diagnosis and had a higher frequency and mean number of tumors, supporting the correlation between nonsense and frameshift mutations and severe NF2. When each family was considered as an independent random event, statistically significant differences between the two groups were observed only for mean ages at onset and at diagnosis. A larger data set is needed to resolve these discrepancies. We observed retinal hamartomas and/or epiretinal membranes in nine patients from five families with four different nonsense mutations. This finding, which may represent a new genotype-phenotype correlation, merits further study.

Adolescent↗

PubMed1996

[Molecular genetic analysis--a new stage in the study of hereditary diseases of the central nervous system].

Molecular genetics is currently the most powerful tool for studying hereditary diseases of the central nervous system: Huntington's disease, dopa-nonresponsive dystonia, Friedreich's disease, etc. The review presents the most important results obtained in this field by the Department of Neurogenetics, Institute of Neurology, in collaboration with several Russian and foreign research institutes. The authors were the first to perform a molecular analysis of mutations and haplotypes in Huntington's disease, dopa-nonresponsive dystonia, Wilson's disease and studied the frequencies of various mutations and main genotype-phenotype correlations in the Russian population. The first direct diagnosis of Huntington's disease in Russia, as well as indirect diagnosis of Friedreich's disease, dopa-nonresponsive dystonia and Wilson's disease have been made. The authors began to investigate trinucleotide repeat expansion in dominant spinocerebellar ataxias and related disorders. The Department of Neurogenetics collected a valuable bank of DNA samples, which is sufficient to perform linkage analysis in essential tremor, novel forms of congenital cerebellar atrophy and progressive muscular atrophy.

Central Nervous System Diseases↗

PubMed1996

Truncation at conserved terminal regions of BRCA1 protein is associated with highly proliferating hereditary breast cancers.

The existence of two subgroups of BRCA1-associated breast cancer (BC) families has been recently posited: the first with highly proliferating tumors, and the second composed of cases with a low proliferation rate. Our aim was to test whether the proliferation rate of BRCA1-associated breast cancers was affected by the site of the germ line mutation in the BRCA1 gene. We analyzed the distribution of the mitotic index, a histoprognostic grade component shown to segregate in families, matching for germ line mutation location in a series of 28 breast cancers from 20 kindreds. We observed a prevalence of highly proliferating tumors when the mutation occurs in the two terminal conserved domains of the BRCA1 protein, ie., in the amino and carboxyl termini (P = 0.0024). Our data provide evidence for a genotype-phenotype correlation and along with their strong conservation during evolution argue for the importance of these two regions in the control of mammary cell growth.

Alleles↗