Classic Ehlers-Danlos syndrome is a heritable connective tissue disorder characterized by skin hyperextensibility, fragile and soft skin, delayed wound healing with formation of atrophic scars, easy ...bruising, and generalized joint hypermobility. It comprises Ehlers-Danlos syndrome type I and Ehlers-Danlos syndrome type II, but it is now apparent that these form a continuum of clinical findings and differ only in phenotypic severity. It is currently estimated that approximately 50% of patients with a clinical diagnosis of classic Ehlers-Danlos syndrome harbor mutations in the COL5A1 and the COL5A2 gene, encoding the α1 and the α2-chain of type V collagen, respectively. However, because no prospective molecular studies of COL5A1 and COL5A2 have been performed in a clinically well-defined patient group, this number may underestimate the real proportion of patients with classic Ehlers-Danlos syndrome harboring a mutation in one of these genes. In the majority of patients with molecularly characterized classic Ehlers-Danlos syndrome, the disease is caused by a mutation leading to a nonfunctional COL5A1 allele and resulting in haploinsufficiency of type V collagen. A smaller proportion of patients harbor a structural mutation in COL5A1 or COL5A2, causing the production of a functionally defective type V collagen protein. Most mutations identified so far result in a reduced amount of type V collagen in the connective tissues available for collagen fibrillogenesis. Inter- and intrafamilial phenotypic variability is observed, but no genotype-phenotype correlations have been observed. No treatment for the underlying defect is presently available for Ehlers-Danlos syndrome. However, a series of preventive guidelines are applicable.
Mutation screening of the breast and ovarian cancer–predisposition genes
BRCA1 and
BRCA2 is becoming an increasingly important part of clinical practice. Classification of rare nontruncating sequence ...variants in these genes is problematic, because it is not known whether these subtle changes alter function sufficiently to predispose cells to cancer development. Using data from the Myriad Genetic Laboratories database of nearly 70,000 full-sequence tests, we assessed the clinical significance of 1,433 sequence variants of unknown significance (VUSs) in the BRCA genes. Three independent measures were employed in the assessment: co-occurrence in
trans of a VUS with known deleterious mutations; detailed analysis, by logistic regression, of personal and family history of cancer in VUS-carrying probands; and, in a subset of probands, an analysis of cosegregation with disease in pedigrees. For each of these factors, a likelihood ratio was computed under the hypothesis that the VUSs were equivalent to an “average” deleterious mutation, compared with neutral, with respect to risk. The likelihood ratios derived from each component were combined to provide an overall assessment for each VUS. A total of 133 VUSs had odds of at least 100:1 in favor of neutrality with respect to risk, whereas 43 had odds of at least 20:1 in favor of being deleterious. VUSs with evidence in favor of causality were those that were predicted to affect splicing, fell at positions that are highly conserved among BRCA orthologs, and were more likely to be located in specific domains of the proteins. In addition to their utility for improved genetics counseling of patients and their families, the global assessment reported here will be invaluable for validation of functional assays, structural models, and
in silico analyses.
Testing for germline mutations in BRCA1/2 is standard for select patients with breast cancer to guide clinical management. Next-generation sequencing (NGS) allows testing for mutations in additional ...breast cancer predisposition genes. The frequency of germline mutations detected by using NGS has been reported in patients with breast cancer who were referred for BRCA1/2 testing or with triple-negative breast cancer. We assessed the frequency and predictors of mutations in 25 cancer predisposition genes, including BRCA1/2, in a sequential series of patients with breast cancer at an academic institution to examine the utility of genetic testing in this population.
Patients with stages I to III breast cancer who were seen at a single cancer center between 2010 and 2012, and who agreed to participate in research DNA banking, were included (N = 488). Personal and family cancer histories were collected and germline DNA was sequenced with NGS to identify mutations.
Deleterious mutations were identified in 10.7% of women, including 6.1% in BRCA1/2 (5.1% in non-Ashkenazi Jewish patients) and 4.6% in other breast/ovarian cancer predisposition genes including CHEK2 (n = 10), ATM (n = 4), BRIP1 (n = 4), and one each in PALB2, PTEN, NBN, RAD51C, RAD51D, MSH6, and PMS2. Whereas young age (P < .01), Ashkenazi Jewish ancestry (P < .01), triple-negative breast cancer (P = .01), and family history of breast/ovarian cancer (P = .01) predicted for BRCA1/2 mutations, no factors predicted for mutations in other breast cancer predisposition genes.
Among sequential patients with breast cancer, 10.7% were found to have a germline mutation in a gene that predisposes women to breast or ovarian cancer, using a panel of 25 predisposition genes. Factors that predict for BRCA1/2 mutations do not predict for mutations in other breast/ovarian cancer susceptibility genes when these genes are analyzed as a single group. Additional cohorts will be helpful to define individuals at higher risk of carrying mutations in genes other than BRCA1/2.
Vertebrate collagen fibrils are heterotypically composed of a quantitatively major and minor fibril collagen. In non-cartilaginous tissues, type I collagen accounts for the majority of the collagen ...mass, and collagen type V, the functions of which are poorly understood, is a minor component. Type V collagen has been implicated in the regulation of fibril diameter, and we reported recently preliminary evidence that type V collagen is required for collagen fibril nucleation (Wenstrup, R. J., Florer, J. B., Cole, W. G., Willing, M. C., and Birk, D. E. (2004) J. Cell. Biochem. 92, 113–124). The purpose of this study was to define the roles of type V collagen in the regulation of collagen fibrillogenesis and matrix assembly. Mouse embryos completely deficient in pro-α1(V) chains were created by homologous recombination. The col5a1–/– animals die in early embryogenesis, at approximately embryonic day 10. The type V collagen-deficient mice demonstrate a virtual lack of collagen fibril formation. In contrast, the col5a1+/– animals are viable. The reduced type V collagen content is associated with a 50% reduction in fibril number and dermal collagen content. In addition, relatively normal, cylindrical fibrils are assembled with a second population of large, structurally abnormal collagen fibrils. The structural properties of the abnormal matrix are decreased relative to the wild type control animals. These data indicate a central role for the evolutionary, ancient type V collagen in the regulation of fibrillogenesis. The complete dependence of fibril formation on type V collagen is indicative of the critical role of the latter in early fibril initiation. In addition, this fibril collagen is important in the determination of fibril structure and matrix organization.
Purpose Hereditary factors play an important role in colorectal cancer (CRC) risk, yet the prevalence of germline cancer susceptibility gene mutations in patients with CRC unselected for high-risk ...features (eg, early age at diagnosis, personal/family history of cancer or polyps, tumor microsatellite instability MSI, mismatch repair MMR deficiency) is unknown. Patients and Methods We recruited 1,058 participants who received CRC care in a clinic-based setting without preselection for age at diagnosis, personal/family history, or MSI/MMR results. All participants underwent germline testing for mutations in 25 genes associated with inherited cancer risk. Each gene was categorized as high penetrance or moderate penetrance on the basis of published estimates of the lifetime cancer risks conferred by pathogenic germline mutations in that gene. Results One hundred five (9.9%; 95% CI, 8.2% to 11.9%) of 1,058 participants carried one or more pathogenic mutations, including 33 (3.1%) with Lynch syndrome (LS). Twenty-eight (96.6%) of 29 available LS CRCs demonstrated abnormal MSI/MMR results. Seventy-four (7.0%) of 1,058 participants carried non-LS gene mutations, including 23 (2.2%) with mutations in high-penetrance genes (five APC, three biallelic MUTYH, 11 BRCA1/2, two PALB2, one CDKN2A, and one TP53), 15 of whom lacked clinical histories suggestive of their underlying mutation. Thirty-eight (3.6%) participants had moderate-penetrance CRC risk gene mutations (19 monoallelic MUTYH, 17 APC*I1307K, two CHEK2). Neither proband age at CRC diagnosis, family history of CRC, nor personal history of other cancers significantly predicted the presence of pathogenic mutations in non-LS genes. Conclusion Germline cancer susceptibility gene mutations are carried by 9.9% of patients with CRC. MSI/MMR testing reliably identifies LS probands, although 7.0% of patients with CRC carry non-LS mutations, including 1.0% with BRCA1/2 mutations.
Background & Aims Multigene panels are commercially available tools for hereditary cancer risk assessment that allow for next-generation sequencing of numerous genes in parallel. However, it is not ...clear if these panels offer advantages over traditional genetic testing. We investigated the number of cancer predisposition gene mutations identified by parallel sequencing in individuals with suspected Lynch syndrome. Methods We performed germline analysis with a 25-gene, next-generation sequencing panel using DNA from 1260 individuals who underwent clinical genetic testing for Lynch syndrome from 2012 through 2013. All patients had a history of Lynch syndrome–associated cancer and/or polyps. We classified all identified germline alterations for pathogenicity and calculated the frequencies of pathogenic mutations and variants of uncertain clinical significance (VUS). We also analyzed data on patients’ personal and family history of cancer, including fulfillment of clinical guidelines for genetic testing. Results Of the 1260 patients, 1112 met National Comprehensive Cancer Network (NCCN) criteria for Lynch syndrome testing (88%; 95% confidence interval CI, 86%–90%). Multigene panel testing identified 114 probands with Lynch syndrome mutations (9.0%; 95% CI, 7.6%−10.8%) and 71 with mutations in other cancer predisposition genes (5.6%; 95% CI, 4.4%−7.1%). Fifteen individuals had mutations in BRCA1 or BRCA2 ; 93% of these met the NCCN criteria for Lynch syndrome testing and 33% met NCCN criteria for BRCA1 and BRCA2 analysis ( P = .0017). An additional 9 individuals carried mutations in other genes linked to high lifetime risks of cancer (5 had mutations in APC , 3 had bi-allelic mutations in MUTYH , and 1 had a mutation in STK11 ); all of these patients met NCCN criteria for Lynch syndrome testing. A total of 479 individuals had 1 or more VUS (38%; 95% CI, 35%–41%). Conclusions In individuals with suspected Lynch syndrome, multigene panel testing identified high-penetrance mutations in cancer predisposition genes, many of which were unexpected based on patients’ histories. Parallel sequencing also detected a high number of potentially uninformative germline findings, including VUS.
CONTEXT Patients with multiple colorectal adenomas may carry germline mutations in the APC or MUTYH genes. OBJECTIVES To determine the prevalence of pathogenic APC and MUTYH mutations in patients ...with multiple colorectal adenomas who had undergone genetic testing and to compare the prevalence and clinical characteristics of APC and MUTYH mutation carriers. DESIGN, SETTING, AND PARTICIPANTS Cross-sectional study conducted among 8676 individuals who had undergone full gene sequencing and large rearrangement analysis of the APC gene and targeted sequence analysis for the 2 most common MUTYH mutations (Y179C and G396D) between 2004 and 2011. Individuals with either mutation underwent full MUTYH gene sequencing. APC and MUTYH mutation prevalence was evaluated by polyp burden; the clinical characteristics associated with a pathogenic mutation were evaluated using logistic regression analyses. MAIN OUTCOME MEASURE Prevalence of pathogenic mutations in APC and MUTYH genes. RESULTS Colorectal adenomas were reported in 7225 individuals; 1457 with classic polyposis (≥100 adenomas) and 3253 with attenuated polyposis (20-99 adenomas). The prevalence of pathogenic APC and biallelic MUTYH mutations was 95 of 119 (80% 95% CI, 71%-87%) and 2 of 119 (2% 95% CI, 0.2%-6%), respectively, among individuals with 1000 or more adenomas, 756 of 1338 (56% 95% CI, 54%-59%) and 94 of 1338 (7% 95% CI, 6%-8%) among those with 100 to 999 adenomas, 326 of 3253 (10% 95% CI, 9%-11%) and 233 of 3253 (7% 95% CI, 6%-8%) among those with 20 to 99 adenomas, and 50 of 970 (5% 95% CI, 4%-7%) and 37 of 970 (4% 95% CI, 3%-5%) among those with 10 to 19 adenomas. Adenoma count was strongly associated with a pathogenic mutation in multivariable analyses. CONCLUSIONS Among patients with multiple colorectal adenomas, pathogenic APC and MUTYH mutation prevalence varied considerably by adenoma count, including within those with a classic polyposis phenotype. APC mutations predominated in patients with classic polyposis, whereas prevalence of APC and MUTYH mutations was similar in attenuated polyposis. These findings require external validation.
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