Biallelic deleterious BRCA1 mutations in a woman with early-onset ovarian cancer

BRCA1 and BRCA2 are the most important breast and ovarian cancer susceptibility genes. Biallelic mutations in BRCA2 can lead to Fanconi anemia and predisposition to cancers, whereas biallelic BRCA1 mutations have not been confirmed, presumably because one wild-type BRCA1 allele is required during embryogenesis. This study describes an individual who was diagnosed with ovarian carcinoma at age 28 and found to have one allele with a deleterious mutation in BRCA1, c.2457delC (p.Asp821Ilefs*25), and a second allele with a variant of unknown significance in BRCA1, c.5207T>C (p.Val1736Ala). Medical records revealed short stature, microcephaly, developmental delay, and significant toxicity from chemotherapy. BRCA1 p.Val1736Ala cosegregated with cancer in multiple families, associated tumors showed loss of wild-type BRCA1, and BRCA1 p.Val1736Ala showed reduced DNA damage localization. These findings represent the first validated example of biallelic deleterious human BRCA1 mutations and have implications for the interpretation of genetic test results.

SIGNIFICANCE

Accurate assessment of genetic testing data for BRCA1 mutations is essential for clinical monitoring and treatment strategies. Here, we report the fi rst validated example of an individual with biallelic BRCA1 mutations, early-onset ovarian cancer, and clinically significant hypersensitivity to chemotherapy.

Recurrent dominant mutations affecting two adjacent residues in the motor domain of the monomeric kinesin KIF22 result in skeletal dysplasia and joint laxity

Spondyloepimetaphyseal dysplasia with joint laxity, leptodactylic type (lepto-SEMDJL, aka SEMDJL, Hall type), is an autosomal dominant skeletal disorder that, in spite of being relatively common among skeletal dysplasias, has eluded molecular elucidation so far. We used whole-exome sequencing of five unrelated individuals with lepto-SEMDJL to identify mutations in KIF22 as the cause of this skeletal condition. Missense mutations affecting one of two adjacent amino acids in the motor domain of KIF22 were present in 20 familial cases from eight families and in 12 other sporadic cases. The skeletal and connective tissue phenotype produced by these specific mutations point to functions of KIF22 beyond those previously ascribed functions involving chromosome segregation. Although we have found Kif22 to be strongly upregulated at the growth plate, the precise pathogenetic mechanisms remain to be elucidated.

Molecular analysis of pheochromocytoma after maternal transmission of SDHD mutation elucidates mechanism of parent-of-origin effect

CONTEXT

Pheochromocytoma/paraganglioma occurs almost exclusively after paternal transmission of succinate dehydrogenase D (SDHD) mutations. This parent-of-origin effect has not been fully explained but is accompanied by obligate loss of the maternal copy of chromosome 11. Loss of wild-type SDHD and an additional imprinted gene (hypothesized to be H19) appears necessary for tumor formation. Two previous reports suggested tumor formation after maternal transmission of SDHD mutation, but histological and molecular characterization was unavailable.

OBJECTIVE

We report the first kindred in which histologically confirmed pheochromocytoma/paraganglioma occurred after maternal transmission of an SDHD mutation and investigate the molecular mechanism of tumor formation.

DESIGN

The design of the investigation was the study of a three-generation family with SDHD c.242C>T (p.Pro81Leu) mutation.

RESULTS

The index patient had a histologically confirmed pheochromocytoma and an identical SDHD germline mutation (p.Pro81Leu) to her mother (who had a glomus jugulare tumor) and paraganglioma tissue from her maternal grandfather. Tumor DNA from the index patient revealed loss of heterozygosity (LOH) at 11q23, causing loss of the wild-type paternal SDHD allele and LOH affecting maternal 11p15, including H19. These two regions of LOH were separated by a region exhibiting clearly retained heterozygosity, including SDHAF2, a recently reported paraganglioma susceptibility gene.

CONCLUSIONS

Tumor formation can occur after maternal transmission of SDHD, a finding with important clinical implications for SDHD families. Tumor formation in SDHD mutation requires the loss of both the wild-type SDHD allele and maternal 11p15, leading to the predominant but now not exclusive pattern of disease inheritance after paternal SDHD transmission.

Mutations in TFAP2B cause Char syndrome, a familial form of patent ductus arteriosus

Char syndrome is an autosomal dominant trait characterized by patent ductus arteriosus, facial dysmorphism and hand anomalies. Using a positional candidacy strategy, we mapped TFAP2B, encoding a transcription factor expressed in neural crest cells, to the Char syndrome critical region and identified missense mutations altering conserved residues in two affected families. Mutant TFAP2B proteins dimerized properly in vitro, but showed abnormal binding to TFAP2 target sequence. Dimerization of both mutants with normal TFAP2B adversely affected transactivation, demonstrating a dominant-negative mechanism. Our work shows that TFAP2B has a role in ductal, facial and limb development and suggests that Char syndrome results from derangement of neural-crest-cell derivatives.

The prenatal exclusion test for Huntington's disease: experience in the west of Scotland, 1986-1993

Information about the prenatal exclusion test for Huntington's disease (HD) has been given to an unselected series of couples who attended the genetic counselling clinic from 1986 onwards. Ten couples underwent 13 prenatal tests during this period with expressed intention of stopping a pregnancy if the result indicated a high risk (almost 50%) that the fetus carried the HD gene. Nine fetuses at nearly 50% risk of carrying the HD gene were identified but only six such pregnancies were terminated. In each of three high risk pregnancies which continued, the mother made a "final hour" decision not to undergo the scheduled, first trimester termination. In our experience, late reversal of a previous decision to undergo first trimester pregnancy termination for a genetic indication is uniquely frequent among couples who have undergone the prenatal exclusion test for HD.

A large family with patent ductus arteriosus and unusual face

A large family is described in which patent ductus arteriosus in association with an unusual facial appearance affected nine family members in three generations. The segregation pattern suggests autosomal dominant inheritance with incomplete penetrance with respect to the PDA. The facial features included a broad, high forehead, flat profile, and short nose with a broad, flattened tip.

The angiotensin I converting enzyme gene and predisposition to high blood pressure

Phenotypic abnormalities of the renin-angiotensin system have been associated with the predisposition to high blood pressure. The angiotensin I converting enzyme (ACE) gene has been implicated as a candidate gene. We examined the distribution of common alleles of the ACE gene and measured circulating components of the renin-angiotensin system and urinary sodium excretion in 170 young Caucasian adults with contrasting genetic predisposition to high blood pressure. Predisposition was defined on the basis of personal and parental blood pressure levels by using the four corners sampling method. Young adults with greatest predisposition who had high blood pressure and two parents with high blood pressure did not show any significant difference in the distribution of the markers of the ACE gene, either as genotype or allele frequencies, when compared with young adults with least predisposition who had low blood pressure and two parents with low blood pressure. Offspring with urinary sodium excretion above the median (143.4 mmol per day) also showed no significant differences in the distribution of ACE alleles or genotype between groups. Different genotypes were associated with different average serum ACE concentrations (p < 0.0001), but plasma angiotensin II and aldosterone showed no significant variation with ACE genotype. These results suggest that in a group of Caucasians selected from the general population, the ACE gene is not associated with genetic predisposition to high blood pressure. In this population common ACE gene allelic markers would not be useful indexes of susceptibility to hypertension.

Abnormalities of glucocorticoid metabolism and the renin???angiotensin system: a four-corners approach to the identification of genetic determinants of blood pressure

AIM

To assess the feasibility and utility of a new method to identify factors associated with increased predisposition to high blood pressure in young people.

SUBJECTS

Eight hundred and sixty-four people aged 16-24 years and their parents.

SETTING

Ladywell Medical Centre, Edinburgh, Scotland, UK.

METHOD

Blood pressure was measured in 864 young adults and in both of their parents. Four groups of approximately 50 offspring were selected from the corners of a scatter diagram, with offspring blood pressure scores on one axis and combined parental blood pressure scores on the other. Blood and urine samples were taken for biochemical and genetic analyses.

RESULTS

Two groups of offspring had parents with high blood pressure and two groups had parents with low blood pressure. When parental blood pressure was low, comparison of offspring with high and low blood pressure revealed significantly higher mean body mass index in offspring with high blood pressure, but no significant elevation of biochemical or hormonal variables. When parental blood pressure was high, comparison of offspring with high and low blood pressure also revealed a significant difference in body mass index, but in addition, offspring with high blood pressure and high parental blood pressure had higher levels of angiotensinogen, cortisol and 18-OH corticosterone. Restriction fragment length polymorphism analysis revealed that 27% of offspring at the greatest genetic risk (high personal and parental blood pressure) were homozygous for the larger allele of the glucocorticoid receptor gene compared with only 9% of those at lowest genetic risk (low personal and parental blood pressure).

CONCLUSION

The combined biochemical and genetic findings suggest that abnormalities of glucocorticoid metabolism and the renin-angiotensin system may help to explain genetic predisposition to high blood pressure. The new sampling method is practicable and could be applied to the investigation of other continuously distributed variables which show familial aggregation.

Dyskeratosis congenita

Images

COMIC II in the Automotive Industry

The new Colorant Mixture Computer (COMIC II) has been designed as a tool for use in matching and controlling color production. It does not replace a trained colorist, but frees him of routine color matching problems. Some of the theory and practice of COMIC II applications in the automotive industry are described.