MYH Genes Research Articles

Double Take

Purpose: A 47-year-old woman with history of GERD on chronic PPI and hyperplastic colon polyps presents to GI clinic with iron deficiency anemia of unknown etiology. She has a family history significant for a brother with a Schatzki's ring of the esophagus as well as Barrett's esophagus, a father with colon cancer detected at age 50, two paternal uncles with colonoscopies revealing less than 100 polyps, a paternal great-grandfather with colon cancer, and a maternal grandfather with gastric cancer. Patient's hemoglobin and hematocrit were 10.5 g/dL and 31.6%, respectively. Iron studies revealed an iron level of 25 ug/dL, TIBC of 488 ug/dL, ferritin of 6 ng/ml, transferrin of 390 mg/dL, and transferrin saturation of 5%. Colonoscopy revealed a sessile, 3 mm polyp in the ascending colon and a sessile, 4 mm polyp in the rectum both with biopsy results consistent with a hyperplastic polyp. EGD revealed a mild Schatzki ring in the lower third of the esophagus, a medium-sized hiatal hernia, and 30–50, 5 to 30 mm pedunculated and sessile polyps with no stigmata of recent bleeding in the gastric antrum and body of the stomach. The examined duodenum was normal. Histology confirmed these were fundic gland polyps. Video capsule endoscopy revealed multiple large pedunculated and sessile polyps with no bleeding or stigmata of recent bleeding in the gastric body, fundus and antrum. The patient was evaluated for genetic mutations of the APC or MYH genes because of the multiple, large fundic gland polyps and her family history of colon cancer. Genetic testing came back negative for any mutations in the APC or MYH genes. Ultimately, it was felt that the patient's multiple polyps were secondary to chronic PPI use and were not secondary to malignancy. Polyps are often incidentally discovered on endoscopy and should not simply be overlooked. They require a “double take”. Biopsy is necessary for histological evaluation. When multiple gastric polyps are found, particularly to the degree in this case, further evaluation should be undertaken, regardless of histologic type. Assessing the possibility of genetic mutations that could predispose to GI malignancy is reasonable. APC or MYH gene mutations may be revealed which correlate highly with FAP. In addition, there is a clear correlation between fundic gland polyps and FAP. This could have serious implications for a patient leading to colon cancer. Suddenly, the incidental finding of a gastric polyp which may have been overlooked is very significant. In conclusion, gastric polyps need diagnostic evaluation beyond what is seen during endoscopy which is a change from the current practice during many endoscopies. Methods: N/A Results: N/A Conclusion: N/A

Patient preferences regarding recontact by cancer genetics clinicians

Ongoing advances in cancer genetics lead to new opportunities for early disease detection, predictive genetic testing and potential interventions. Limited information exists on patient preferences concerning recontact to provide updated information. We evaluated colon cancer genetics patient preferences concerning recontact about advances in medical genetics. Information was mailed to 851 individuals seen at the Colon Cancer Risk Assessment Clinic at the Johns Hopkins Hospital and to participants in a colon cancer gene testing study seen during an 8-year period. Information provided included description of advances in gene testing technology, discovery of MSH6 and MYH genes, detailed fact sheets and a survey of patient preferences for notification and potential uses of new information. Most patients wanted an ongoing relationship with genetics providers (63%), reinitiated by genetics providers (65%) and contact only with information specifically relevant to them (51%). Most preferred personalized letters as the means of contact (55%). Reasons for and against recontact and circumstances in which individuals would pursue additional genetic testing were also tabulated. There were few statistically significant differences in the responses between clinic and study participants. Patients evaluated in a colon cancer risk assessment clinic want updated information at a rate similar to those who participated in a colon cancer gene testing study. These findings have implications for the consultative nonlongitudinal nature of such clinics and suggest patient preferences for personally-tailored information could be labor intensive.

Germline mutations and polymorphic variants in MMR, E‐cadherin and MYH genes associated with familial gastric cancer in Jiangsu of China

Germline mutations in MSH2, MLH1, E-cadherin and MutY (MYH) genes have been implicated in the occurrence of gastric cancer (GC). Epidemiological investigation was performed by recruiting patients with GC onset during 2002 in Jiangsu province, China. We identified suspected hereditary GC patients based on either the GC family history or GC onset at early ages. We have screened germline variations in 101 suspected hereditary GC patients at the coding sequences of MSH2, MLH1, E-cadherin and MYH genes with polymerase chain reaction-denaturing high-performance liquid chromatography (PCR-DHPLC) analysis and DNA sequencing. The result showed that about 40% of patients carried germline variations, predominantly with missense mutations. Of the variations detected are 2 base pair substitutions, c.53C > T and c.74G > A, which is predicted to generate missense mutations of p.Pro18Leu and p.Gly25Asp, respectively, and occurred at the same allele of MYH gene. The frequency of variant haplotype T/A in patients was higher than that in the control group (p = 0.021, odds ratio [OR] = 4.43, 95% confidence interval [95% CI] = 1.33-14.72). Difference in the frequency of the silent mutation p.Asn751Asn in E-cadherin gene was also found between patients and controls (p = 0.009, OR = 2.54, 95% CI = 1.30-4.95). Moreover, 6 types of variations were detected in MSH2 and MLH1 genes in 14 of 101 patients. Most of them occurred at exon7 of MSH2, frequently c.1168C > T, resulting in mutation of p.Leu390Phe. In summary, germline mutation at MSH2, MLH1, E-cadherin and MYH genes is a frequent event in the familial GC. They may form a genetic basis for the familial GC susceptibility in Chinese population.

Diversity in transcriptional start site selection and alternative splicing affects the 5′-UTR of mouse striated muscle myosin transcripts

We have analyzed nearly 2,000 myosin heavy chain gene (Myh) clones representing over 30 different transcripts from seven of eight striated muscle Myh genes expressed in mouse. We also report the transcriptional start sites (TSS) for the mouse developmental Myh genes. The data reveal a previously unknown diversity of TSSs and 5'-end alternative splicing in these transcripts. The cardiac Myh6 gene had two major TSSs. Use of the major downstream site led to an alternatively spliced second exon. Each of the other Myh genes had one major TATA-directed TSS and one or more minor alternative TSSs, some associated with alternative splicing. The minor transcripts were associated with polysomes and their spatial-temporal expression largely mirrored that of the major transcripts in wild-type, Myh1 null, Myh4 null, injured, and uninjured muscle, except that one form of Myh7, detected in heart, was not detected in diaphragm, and the ratio of the two major Myh6 transcripts varied in some circumstances. These findings indicate that alternative TSS usage and alternative splicing in the 5'-UTR are a general feature of murine Myh gene expression and that Myh gene regulation is more complex than previously appreciated.

Cyclooxygenase-2 Expression in FAP Patients Carrying Germ Line MYH Mutations

Familial adenomatous polyposis (FAP) is an autosomal condition caused by inherited mutations in the adenomatous polyposis coli (APC) or in the MYH genes. Clinical trials have established that nonsteroidal anti-inflammatory drugs (NSAID) are effective in preventing the development as well as reducing the size and decreasing the number of adenomas in FAP patients. Our aim was to evaluate the cyclooxygenase-2 (COX-2) expression in surgical specimens from patients with no evidence of germ line APC mutations but carrying germ line MYH mutations. COX-2 expression was evaluated through immunohistochemical and mRNA analysis in carcinomas, adenomas, and healthy mucosa from six patients carrying germ line biallelic MYH mutations. A modulation of COX-2 expression from adenoma (lower level) to carcinoma (higher level) was observed in all patients by both immunohistochemical and mRNA analysis. Moreover, patients with MYH mutations showed a weak COX-2 expression in the whole colorectal mucosa, as for classic FAP patients carrying germ line APC mutations. All together, our data suggest that biallelic MYH patients might benefit from NSAID treatment, because in these patients COX-2 is overexpressed in the whole colorectal mucosa, a finding possibly related to the interplay between COX-2 and APC protein being the APC gene a common target of mutations in MYH patients.

Genetic Testing for Inherited Colon Cancer

The genes associated with each of the inherited syndromes of colon cancer have now been identified, and genetic testing is available for diagnosis. These syndromes include familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, Peutz-Jeghers syndrome, juvenile polyposis syndrome, and, possibly, Cowden's syndrome. Clinical genetic testing approaches have been developed for each of these syndromes and are now a part of accepted clinical care. Disease-causing mutations can be found in the majority of families affected with one of the inherited syndromes, and, most importantly, once a mutation is found in an index case of the family, relatives can be tested for the presence or absence of that mutation with near 100% accuracy. Cancer screening and management in syndrome families is then based on the results of genetic testing. For the physician to order and properly interpret genetic tests, a basic understanding of the types of mutations that lead to inherited disease and the methods for detecting them is vital. These issues will be presented. Additional clinical issues somewhat unique to genetic testing include genetic counseling and informed consent for genetic testing, both of which will also be reviewed. Often the most difficult aspect of genetic testing is deciding which patients and families should undergo the testing. Furthermore, this issue is quite specific for each of the syndromes. Thus, following presentation of general principles of selection for genetic testing, a detailed approach for identifying persons who should undergo testing for each of the individual syndromes will be given, together with relevant descriptions of the syndromes. Finally, the ongoing work to discover new and possibly more common but less penetrant colon cancer susceptibility genes that cause common familial colon cancer will be presented.

Mutations ofAPC andMYH in unrelated Italian patients with adenomatous polyposis coli

The analysis of APC and MYH mutations in adenomatous polyposis coli patients should provide clues about the genetic heterogeneity of the syndrome in human populations. The entire coding region and intron-exon borders of the APC and MYH genes were analyzed in 60 unrelated Italian adenomatous polyposis coli patients. APC analysis revealed 26 point mutations leading to premature termination, one missense variant and one deletion spanning the entire coding region in 32 unrelated patients. Novel truncating point mutations included c.1176_1177insT (p.His393_PhefsX396), c.1354_1355del (p.Val452_SerfsX458), c.2684C>A (p.Ser895X), c.2711_2712del (p.Arg904_LysfsX910), c.2758_2759del (p.Asp920_CysfsX922), c.4192_4193del (p.Ser1398_SerfsX1407), c.4717G>T (p.Glu1573X) and a novel cryptic APC exon 6 splice site. MYH analysis revealed nine different germline variants in nine patients, of whom five were homozygotes or compound heterozygotes. The mutations included 4 novel MYH missense variants (c.692G>A, p.Arg231His; c.778C>T, p.Arg260Trp; c.1121T>C, p.Leu374Pro; and c.1234C>T, p.Arg412Cys) affecting conserved amino acid residues in the ENDO3c or NUDIX domains of the protein and one novel synonymous change (c.672C>T, p.Asn224Asn). Genotype-phenotype correlations were found in carriers of APC mutations but not in carriers of biallelic MYH mutations, except for a negative correlation with low number of polyps. A distinctive characteristic of patients negative for APC and MYH mutations was a significantly (p<0.0001) older age at diagnosis compared to patients with APC mutations. Moreover, the proportion of cases with an attenuated polyposis phenotype was higher (p = 0.0008) among patients negative for APC and MYH mutations than among carriers of APC or biallelic MYH mutations.

High frequency of MYH gene mutations in a subset of patients with familial adenomatous polyposis

Background & Aims : Inherited colorectal polyposis has been linked to constitutive mutations of the APC tumor suppressor gene. Recently, germline mutations in the base excision repair gene MYH have been associated with a recessively inherited form of the disease. The aim of this study was to evaluate germline mutation frequencies of both MYH and APC susceptibility genes in Italian patients with attenuated familial adenomatous polyposis. Methods : The analysis was performed in 14 unrelated patients by using the protein truncation test for APC and genomic DNA sequencing for MYH. Results : Overall, we identified 7 of 14 (50%) mutation carriers. Two patients were heterozygotes for an APC truncating mutation (2 of 14 [14%]), whereas 5 proved to be homozygotes or compound heterozygotes for MYH gene alterations (5 of 14 [36%]). Two MYH missense mutations, Y165C and G382D, already found to be frequent among patients from northern Europe, were also preponderant in our survey. Individuals with APC-associated syndrome showed a dominant family history of polyposis, whereas patients with MYH-associated disease were either apparently sporadic cases or had a family history consistent with recessive inheritance. MYH biallelic mutation carriers were up to 60% (5 of 8) among patients showing at least 30 adenomas and a family history with no vertical transmission of polyposis. Conclusions : On the basis of our data, patients with attenuated familial adenomatous polyposis with >30 adenomas and no obvious vertical transmission of the disease should be considered for MYH gene testing.

Somatic mutations and single nucleotide polymorphisms of base excision repair genes involved in the repair of 8-hydroxyguanine in damaged DNA

To elucidate the involvement of 8-hydroxyguanine (oh 8G) repair genes in human lung carcinogenesis, 47 lung cancer cell lines and 55 primary lung cancers were examined for somatic mutations and genetic polymorphisms in all coding exons of the MYH and APEX genes, and exon 8 of the OGG1 gene by polymerase chain reaction–single strand conformation polymorphism analysis. In the MYH gene, one missense mutation was detected in a cell line, NCI-H157, whereas no mutations were detected in primary cancers. There were no mutations in the APEX and OGG1 genes in the cell lines or primary cancers. Ten single nucleotide polymorphisms (SNPs) were identified, and seven of them were accompanied by amino acid substitutions. Differences in the oh 8G repair activities of MYH, APEX and OGG1 proteins due to somatic mutations and SNPs can be involved in human carcinogenesis.

Smooth Muscle Myosin Heavy Chain Locus (MYH11) Maps to 16p13.13-p13.12 and Establishes a New Region of Conserved Synteny between Human 16p and Mouse 16

The human smooth muscle myosin heavy chain locus (MYH11) was mapped by fluorescence in situ hybridization to the middle of the p arm of chromosome 16 using a genomic cosmid clone containing coding sequences of the gene as probe. Probe from coding sequence, when applied to Southern blots of a panel of hybrids containing different portions of human chromosome 16, localized the gene to 16p13.13-13.12. Coding sequence PCR primers, when used on the DNA from a CHO-mouse hybrid clone mapping panel informative for mouse chromosomes, showed that the gene was located on mouse chromosome 16. These results correct a recent assignment of MYH11 from 16q12.2 to the region of the 16p-arm inversion breakpoint seen in acute myelomonocytic leukemia (AMML) M4Eo and demonstrate that the conflicting data do not result from the presence of additional MYH genes on the q arm of the chromosome. Also, a new region of conserved synteny between human 16p and mouse 16 is established.