Genetics and Natural History of Non-pancreatectomized Patients With Congenital Hyperinsulinism Due to Variants in ABCC8.

CONTEXT: Patients with congenital hyperinsulinism due to ABCC8 variants generally present severe hypoglycemia and those who do not respond to medical treatment typically undergo pancreatectomy. Few data exist on the natural history of non-pancreatectomized patients. OBJECTIVE: This work aims to describe the genetic characteristics and natural history in a cohort of non-pancreatectomized patients with congenital hyperinsulinism due to variants in the ABCC8 gene. METHODS: Ambispective study of patients with congenital hyperinsulinism with pathogenic or likely pathogenic variants in ABCC8 treated in the last 48 years and who were not pancreatectomized. Continuous glucose monitoring (CGM) has been periodically performed in all patients since 2003. An oral glucose tolerance test was performed if hyperglycemia was detected in the CGM. RESULTS: Eighteen non-pancreatectomized patients with ABCC8 variants were included. Seven (38.9%) patients were heterozygous, 8 (44.4%) compound heterozygous, 2 (11.1%) homozygous, and 1 patient carried 2 variants with incomplete familial segregation studies. Seventeen patients were followed up and 12 (70.6%) of them evolved to spontaneous resolution (median age 6.0 ± 4 years; range, 1-14). Five of these 12 patients (41.7%) subsequently progressed to diabetes with insufficient insulin secretion. Evolution to diabetes was more frequent in patients with biallelic variants in the ABCC8 gene. CONCLUSION: The high remission rate observed in our cohort makes conservative medical treatment a reliable strategy for the management of patients with congenital hyperinsulinism due to ABCC8 variants. In addition, a periodic follow-up of glucose metabolism after remission is recommended, as a significant proportion of patients evolved to impaired glucose tolerance or diabetes (biphasic phenotype).

Mutation analysis of the BCCIP gene for breast cancer susceptibility in breast/ovarian cancer families.

OBJECTIVE: About 5%-10% of breast cancer is due to inherited disease predisposition. Currently, mutations in the BRCA1 and BRCA2 genes explain less than 25% of the familial clustering of breast cancer, and additional susceptibility genes are suspected. The BCCIP gene plays an important role in the regulation of gene transcription and cell proliferation and could be involved in the maintenance of genomic integrity. The BCCIP protein binds in mammalian cells to the longest conserved region of the BRCA2 protein and is required for BRCA2 stability and function, making a critical contribution to the function of BRCA2 in mediating homologous recombination. Variants in the BCCIP gene could affect the BRCA2 functionality and be associated to the familial breast/ovarian carcinogenesis. Therefore, BCCIP gene is a potential candidate for being involved in heritable cancer susceptibility. METHODS: We have screened the entire coding region and splice junctions of BCCIP in affected index cases from 215 Spanish breast/ovarian cancer families for germ line defects, using direct sequencing. RESULTS: Mutation analysis revealed 3 different intronic sequence changes. CONCLUSIONS: Based on the in silico and in vitro RNA analyses of these sequence alterations, none of them were predicted to be pathogenic or associated with cancer susceptibility. Our results indicate that BCCIP germ line mutations are unlikely to be a major contributor to familial breast/ovarian cancer risk in our population.

Mutation analysis of the SHFM1 gene in breast/ovarian cancer families.

PURPOSE: About 5-10 % of breast cancer is due to inherited disease predisposition. Currently known susceptibility genes such as BRCA1 and BRCA2 explain less than 25 % of familial aggregation of breast cancer, which suggests the involvement of additional genetic susceptibility. The SHFM1 [split hand/foot malformation (ectrodactyly) type 1] gene plays an important role in the regulation of gene transcription and cell proliferation and may be involved in the maintenance of genomic integrity. It is a potential candidate for being involved in heritable cancer susceptibility due to its biological function. The SHFM1 protein binds in mammalian cells to the longest conserved region of the BRCA2 protein and is required for BRCA2 stability and function, making a critical contribution to the BRCA2 function in mediating homologous recombination. Therefore, variants in the SHFM1 gene could affect the BRCA2 functionality and be associated with the familial breast/ovarian carcinogenesis. METHODS: We have screened the entire coding region and splice junctions of SHFM1 in affected index cases from 369 Spanish breast/ovarian cancer families for germ line defects, using direct sequencing. RESULTS: Mutation analysis revealed seven different sequence changes. Based on the in silico analyses of these sequence alterations, as well as their occurrence in cases and controls, none of them, however, were predicted to be pathogenic or associated with cancer susceptibility. CONCLUSIONS: To our knowledge, this is the most comprehensive study reporting the mutation screening of the SHFM1 gene in familial breast/ovarian cancer cases. No evidence for the association with breast/ovarian cancer was observed.

Novel BRCA1 deleterious mutation (c.1949_1950delTA) in a woman of Senegalese descent with triple-negative early-onset breast cancer.

Limited information exists regarding BRCA1 and BRCA2 genetic testing and genetic diversity in BRCA1 and BRCA2 in sub-Saharan African populations. We report a novel mutation that consists of a deletion of 2 bp (c.1949_1950delTA) in the exon 11 of the BRCA1 gene. This is a frameshift mutation that causes the disruption of the translational reading frame resulting in a premature stop codon downstream in the BRCA1 protein. The mutation was present in a Senegalese woman with a triple-negative breast tumor and a family history of breast cancer.

Identification of a new complex deleterious mutation in exon 18 of the BRCA2 gene in a hereditary male/female breast cancer family.

We report a novel complex mutation that consists of a deletion of 12 bp and an insertion of 2 bp (c.8402_8413del12ins2bp) in the exon 18 of the BRCA2 gene. This is a frameshift mutation that causes a disruption of the translational reading frame resulting in a stop codon downstream in the 2729 position of the BRCA2 protein. The mutation was present in a Spanish hereditary male/female breast cancer family.

A novel de novo BRCA2 mutation of paternal origin identified in a Spanish woman with early onset bilateral breast cancer.

Germ line mutations in either of the two major breast cancer predisposition genes, BRCA1 and BRCA2, account for a significant proportion of hereditary breast/ovarian cancer. Identification of breast cancer patients carrying mutations in any of these genes is primarily based on a positive family history of breast/ovarian cancer or early onset of the disease. In the course of mutation screening of the BRCA1 and BRCA2 genes in a hospital based series of patients with risk factors for hereditary breast/ovarian cancer, we identified a novel germ line mutation in the BRCA2 gene (c.51dupA) in a patient with early onset bilateral breast cancer and no family history of the disease. None of her parents carried the mutation, and paternity was confirmed. Subsequent molecular analysis demonstrated that the mutation was a novel de novo germ line mutation located in the paternal allele of the BRCA2 gene.

The variants BRCA1 IVS6-1G>A and BRCA2 IVS15+1G>A lead to aberrant splicing of the transcripts.

The majority of BRCA1 and BRCA2 deleterious mutations and variants of unknown significance have been identified in genomic DNA and their effects at the mRNA level have not been reported. Our aim was to ascertain the pathological effect of the BRCA1 IVS6-1G>A (c. 302-1G>A) and the BRCA2 IVS15+1G>A (c. 7617+1G>A) variants detected in Spanish breast/ovarian cancer families. Sequencing of cDNA from the BRCA1 IVS6-1G>A allele revealed an inappropriate splicing of exon 7. The analysis of the BRCA2 IVS15+1G>A allele showed the skipping of exon 15. Both alterations predicted the appearance of premature stop codons. Our findings highlight the importance of studying mutations at DNA and RNA levels in order to clarify the effect of the suspected mutation and to provide adequate counseling for breast/ovarian cancer families.