MYH Gene Research Articles

Expression of ovine MYH3 gene and its polymorphisms and association analysis with growth traits in Hu sheep

The growth rate of sheep determines their productivity; the faster the growth rate, the higher the productivity. Sheep growth is usually measured by body weight, which is an important indicator of overall growth, and body size, which reflects body shape and structure. Therefore, in sheep production, the selection and improvement of growth traits is one of the important means to improve production efficiency. In this study, 857 males of Hu sheep were selected to record growth traits, including body weight, height, length, and chest, and cannon circumference at 80, 100, 120, 140, 160 and 180 days of age, as well as live weight before slaughter and carcass weight. Correlation analyses conducted between these growth traits at different stages were significantly correlated with both live weight before slaughter and carcass weight. And the strongest correlation was observed for body weight, while body height showed the weakest correlation. The myosin heavy chain 3 (MYH3) gene in the MYH gene family was selected as the target gene, and a synonymous mutation (MYH3 g.33834192A>G) in the exon 12 region of MYH3 was identified by polymerase chain reaction (PCR) and Sanger sequencing. Further association analysis using competitive allele-specific PCR (KASPar) technique showed that the MYH3 g.33834192A>G locus was significantly (P < 0.05) associated with growth traits (including body weight from 80 to 160 days of age, body height at 80 and 100 days of age, body length at 100 and 140 days of age, chest circumference at 80, 100, 160, and 180 days of age, cannon circumference at 80–140 days of age and carcass weight). Among them, the dominant genotype was GG. Meanwhile, the tissue expression results indicated that the highest level of MYH3 gene expression was found in muscle tissues. Therefore, this locus can be used as a candidate molecular genetic marker for improving growth traits in Hu sheep.

Digoxigenin-labeled RNA probes for untranslated regions enable the isoform-specific gene expression analysis of myosin heavy chains in whole-mount in situ hybridization.

Myosin heavy chains (MyHCs), which are encoded by myosin heavy chain (Myh) genes, are the most abundant proteins in myofiber. Among the 11 sarcomeric Myh isoform genes in the mammalian genome, seven are mainly expressed in skeletal muscle. Myh genes/MyHC proteins share a common role as force producing units with highly conserved sequences, but have distinct spatio-temporal expression patterns. As such, the expression patterns of Myh genes/MyHC proteins are considered as molecular signatures of specific fiber types or the regenerative status of mammalian skeletal muscles. Immunohistochemistry is widely used for identifying MyHC expression patterns; however, this method is costly and is not ideal for whole-mount samples, such as embryos. In situ hybridization (ISH) is another versatile method for the analysis of gene expression, but is not commonly applied for Myh genes, partly because of the highly homologous sequences of Myh genes. Here we demonstrate that an ISH analysis with the untranslated region (UTR) sequence of Myh genes is cost-effective and specific method for analyzing the Myh gene expression in whole-mount samples. Digoxigenin (DIG)-labeled antisense probes for UTR sequences, but not for protein coding sequences, specifically detected the expression patterns of respective Myh isoform genes in both embryo and adult skeletal muscle tissues. UTR probes also revealed the isoform gene-specific polarized localization of Myh mRNAs in embryonic myofibers, which implied a novel mRNA distribution mechanism. Our data suggested that the DIG-labeled UTR probe is a cost-effective and versatile method to specifically detect skeletal muscle Myh genes in a whole-mount analysis.

MYH1F promotes the proliferation and differentiation of chicken skeletal muscle satellite cells into myotubes

In diploid organisms, interactions between alleles determine phenotypic variation. In previous experiments, only MYH1F was found to show both ASE (spatiotemporal allele-specific expression) and TRD (allelic transmission ratio distortion) characteristics in the pectoral muscle by comparing the genome-wide allele lists of hybrid populations (F1) of meat- and egg- type chickens. In addition, MYH1F is a member of the MYH gene family, which plays an important role in skeletal muscle and non-muscle cells of animals, but the specific expression and function of this gene in chickens are still unknown. Therefore, qRT-PCR was used to detect the expression of MYH1F in different tissues of chicken. Proliferation and differentiation of chicken skeletal muscle satellite cells (SMSCs) have been detected by transfection of MYH1F-specific small interfering RNA (siRNA). The results showed that the expression of MYH1F in chicken skeletal muscle was higher than that in other tissues. Combined with CCK-8 assay, EdU assay, immunofluorescence, and Western blot Assay, it was found that MYH1F knockdown could significantly suppress the proliferation of chicken SMSCs and depress the differentiation and fusion of the cells. These results suggest that MYH1F plays a critical role in myogenesis in poultry, which is of great significance for exploring the regulatory mechanisms of muscle development and improving animal productivity.

Whole-genome sequence-based association analyses on an eight-breed crossed heterogeneous stock of pigs reveal the genetic basis of skeletal muscle fiber characteristics

Skeletal muscle fiber characteristics (MFCs) have been extensively studied due to their importance to human health and athletic ability, as well as to the quantity and quality of livestock meat production. Hence, we performed a genome-wide association study (GWAS) on nine muscle fiber traits by using whole genome sequence data in an eight-breed crossed heterogeneous stock pig population. This GWAS revealed 67 quantitative trait loci (QTLs) for these traits. The most significant GWAS signal was detected in the region of Sus scrofa chromosome 12 (SSC12) containing the MYH gene family. Notably, we identified a significant SNP rs322008693 (P = 7.52E-09) as the most likely causal mutation for the total number of muscle fibers (TNMF) QTL on SSC1. The results of EMSA and luciferase assays indicated that the rs322008693 SNP resided in a functional element. These findings provide valuable molecular markers for pig meat production selection as well as for deciphering the genetic mechanisms of the muscle fiber physiology.

Assessment the effect of genomic selection and detection of selective signature in broilers

Due to high selection advances and shortened generation interval, genomic selection (GS) is now an effective animal breeding scheme. In broilers, many studies have compared the accuracy of different GS prediction methods, but few reports have demonstrated phenotypic or genetic changes using GS. In this study, the paternal chicken line B underwent continuous selection for 3 generations. The chicken 55 k SNP chip was used to estimate the genetic parameters and detect genomic response regions by selective sweep analysis. The heritability for body weight (BW), meat production, and abdominal fat traits were ranged from 0.12 to 0.38. A high genetic correlation was found between BW and meat production traits, while a low genetic correlation (<0.1) was found between meat production and abdominal fat traits. Selection resulted in an increase of about 516 g in BW and 140 g in breast muscle weight. Percentage of breast muscle and whole thigh were increased 0.8 to 1.5%. No change was observed in abdominal fat percentage. The genomic estimated breeding value advances was positive for BW and meat production (except whole thigh percentage), while negative for abdominal fat percentage. By selective sweep analysis, 39 common chromosomal regions and 102 protein coding genes were found to be influenced, including MYH1A, MYH1B, and MYH1D of the MYH gene family. Tight junction pathway as well as myosin complex related terms were enriched. This study demonstrates the effective use of GS for improvements in BW and meat production in chicken line B. Further, genomic regions, responsive to intensive genetic selection, were identified to contain genes of the MYH family.

Transcriptome Analyses of In Vitro Exercise Models by Clenbuterol Supplementation or Electrical Pulse Stimulation

Exercise has beneficial effects on human health and is affected by two different pathways; motoneuron and endocrine. For the advancement of exercise research, in vitro exercise models are essential. We established two in vitro exercise models using C2C12 myotubes; EPS (electrical pulse stimulation) for a motoneuron model and clenbuterol, a specific β2 adrenergic receptor agonist, treatment for an endocrine model. For clenbuterol treatment, we found that Ppargc1a was induced only in low glucose media (1 mg/mL) using a 1-h treatment of 30 ng/mL clenbuterol. Global transcriptional changes of clenbuterol treatment were analyzed by RNA-seq and gene ontology analyses and indicated that mitogenesis and the PI3K-Akt pathway were enhanced, which is consistent with the effects of exercise. Cxcl1 and Cxcl5 were identified as candidate myokines induced by adrenaline. As for the EPS model, we compared 1 Hz of 1-pulse EPS and 1 Hz of 10-pulse EPS for 24 h and determined Myh gene expressions. Ten-pulse EPS induced higher Myh2 and Myh7 expression. Global transcriptional changes of 10-pulse EPS were also analyzed using RNA-seq, and gene ontology analyses indicated that CaMK signaling and hypertrophy pathways were enhanced, which is also consistent with the effects of exercise. In this paper, we provided two transcriptome results of in vitro exercise models and these databases will contribute to advances in exercise research.

&lt;p&gt;A Novel Mutation in &lt;em&gt;MYH&lt;/em&gt; Gene Associated with Aggressive Colorectal Cancer in a Child: A Case Report and Review of Literature&lt;/p&gt;

Colorectal cancer is a rare pediatric tumor. Pediatric patients with colorectal cancer present with more aggressive tumor biology and at later stages of the disease, higher proportions of signet ring and mucinous histology, and less differentiation. The effective treatment is same as that received by adults. The overall prognosis of pediatric colorectal cancer is generally poor. Genetic mutations have been identified as the cause of inherited cancer risk in some colorectal cancers. Here, we presented a case of a pediatric patient carrying a maternally derived, heterozygous MYH germline mutation (c.934–2A>G,intron), the mutation was not reported in pediatric patients before. Also, the patient carried somatic mutations of proto-oncogene SMAD4 (R361C) and TP53 (Y234H). The patient underwent surgical resection, chemotherapy and targeted therapy, but the prognosis was not good. We also review the literature to summarize clinical features, gene mutations, management, and outcomes of pediatric colorectal cancer patient. Our results suggest that the genetic mutation of MYH together with somatic mutations of proto-oncogene SMAD4 and TP53 may lead to the early onset colorectal cancer of the patient. Although the overall prognosis of pediatric colorectal cancer is generally poor, the pathogenesis may be related to hereditary genetic mutations as was found with the MYH gene mutation in our case. Genetic screening can provide early diagnosis and improve prognosis.

HSP90 modulates the myosin replacement rate in myofibrils.

Myosin is a major myofibrillar component in skeletal muscles. In myofibrils, ~300 myosin molecules form a single thick filament in which there is constant turnover of myosin. Our previous study demonstrated that the myosin replacement rate is reduced by inhibition of protein synthesis (Ojima K, Ichimura E, Yasukawa Y, Wakamatsu J, Nishimura T, Am J Physiol Cell Physiol 309: C669-C679, 2015); however, additional factors influencing myosin replacement were unknown. Here, we showed that rapid myosin replacement requires heat shock protein 90 (HSP90) activity. We utilized the fluorescence recovery after photobleaching technique to measure the replacement rate of green fluorescent protein-fused myosin heavy chain (GFP-MYH) in myotubes overexpressing HSP90. Intriguingly, the myosin replacement rate was significantly increased in HSP90-overexpressing myotubes, whereas the myosin replacement rate slowed markedly in the presence of an HSP90-specific inhibitor, indicating that HSP90 activity promotes myosin replacement. To determine the mechanism of this effect, we investigated whether HSP90 activity increased the amount of myosin available for incorporation into myofibrils. Strikingly, the gene expression levels of MYHs were significantly elevated by HSP90 overexpression but downregulated by inhibition of HSP90 activity. Cytosolic myosin content was also increased in myotubes overexpressing HSP90. Taken together, our results demonstrate that HSP90 activity facilitates myosin replacement by upregulating MYH gene expression and thereby increasing cytosolic myosin content.

A Rare Case Report of Gardner Syndrome: A Familial Adenomatous Polyposis Variant

Gardner syndrome is a rare autosomal dominant clinical variant of familial adenomatous polyposis (FAP). It is characterized by the prominence of inherited colonic adenomatosis together with osteomas, epidermoid cysts, desmoid tumors, and dental abnormalities. Along with FAP, Gardner syndrome can be explained by the mutation of the APC gene on chromosome 5q21-q22. In addition, the specific mutation of the MYH gene on chromosome 1p34.3-p32.1 may determine the extra-colonic manifestations found in Gardner syndrome, as well as the number, time frame, and malignant potential of the disorder. Due to its rarity, the exact prevalence of Gardner syndrome is unknown, as its statistical prevalence cannot be separated from FAP when considering reported studies. Estimates for the prevalence of the combined syndromes vary from 1 in 6,850 to 1 in 31,250 individuals.Figure 1Figure 2In this case report, we will present a patient with a prior diagnosis of Gardner syndrome that was seen for screening EGD and colonoscopy and was found to have painful, enlarging bilateral breast masses. The patient was also found to have clinically detectable cranial lesions and soft tissue lesions. A right breast mass needle biopsy was performed and resulted positive for fibrous tissue proliferation consistent with desmoid fibromatosis. EGD resulted in innumerable number of polyps within the cardia, fundus, and proximal aspect of the greater curvature as well as several large polyps in the second portion of the duodenum. Colonoscopy resulted in innumerable number of polyps throughout the colon from the cecum to the rectum. Polyps were biopsied during both exams and were positive for inflammatory, hyperplastic polyps in the stomach and tubular adenomas in the duodenum, cecum, and colon. Patients with Gardner syndrome and any FAP-encompassing disease will require regular screening for numerous neoplastic transformations, as presented in this case. A prophylactic colectomy is recommended and unavoidable. It should be performed early in the disease course in order to decrease the patient's risk of colorectal cancer formation. After surgical prophylaxis has been conducted, patients will continue to require lower gastrointestinal surveillance at the anastomosis site as well as lifetime upper gastrointestinal screening based on Spigelman classification. Strict follow-up and surveillance guidelines remain a vital component to the treatment of these patients in order to reduce overall morbidity and mortality.

A Case Report of Gardner’s Syndrome: A Familial Adenomatous Polyposis Variant

Introduction: Gardner syndrome is a rare autosomal dominant clinical variant of familial adenomatous polyposis. It is characterized by the prominence of inherited colonic adenomatosis together with osteomas, epidermoid cysts, desmoid tumors, and dental abnormalities. Along with familial adenomatous polyposis, Gardner syndrome can be explained by the mutation of the APC gene on chromosome 5q21-q22. In addition, the specific mutation of the MYH gene on chromosome 1p34.3-p32.1 may determine the extra-colonic manifestations found in Gardner syndrome, as well as the number, time frame, and malignant potential of the disorder. Due to its rarity, the exact prevalence of Gardner syndrome is unknown, as its statistical prevalence cannot be separated from familial adenomatous polyposis when considering reported studies. Estimates for the prevalence of the combined syndromes vary from 1 in 6,850 to 1 in 31,250 individuals. In this case report, we will present a patient with a prior diagnosis of Gardner syndrome who was seen for screening EGD and colonoscopy, and was found to have enlarging bilateral formed painful breast masses. In addition, the patient was also found to have various lesions biopsied and removed in the past, but continues to have clinically detectable cranial lesions and soft tissue lesions. Right breast mass needle biopsy performed and pathology resulted with fibrous tissue proliferation consistent with desmoid and fibromatosis. EGD resulted in innumerable number of polyps within the cardia, fundus, and proximal aspect of the greater curvature, as well as several large polyps in the second portion of the duodenum. Colonoscopy resulted in innumerable number of polyps throughout the colon from the rectum to the cecum. Polyps were biopsied during both exams, and pathology returned with an inflammatory, hyperplastic polyp in the stomach and tubular adenomas in the duodenum, cecum, and colon. Patients with Gardner syndrome and any familial adenomatous polyposis encompassing disease will require regular screening for numerous neoplastic transformations, as presented in this case. A prophylactic colectomy recommendation is unavoidable, and should be made early within the disease course in order to decrease patient’s risk of colorectal cancer formation. After surgical prophylaxis has been conducted, patients will continue to require lower gastrointestinal surveillance at anastomosis site, based on which surgical operation was performed, as well as lifetime upper gastrointestinal screening at varying intervals based on the Spigelman classification. Strict follow-up and surveillance guidelines remain a vital component to the treatment of these patients in order to reduce their lifetime morbidity and mortality.

Clinical and genetic characteristics of patients with multiple polyposis of the large bowel negative for APC and MYH gene mutations using conventional methods

A genealogical analysis and molecular and clinical investigations were carried out in 19 probands with multiple colorectal adenomas (numbering near 100 or more). Twelve of these patients (63.1%) were negative for the APC and MYH gene mutations using conventional methods. A hereditary form of the disorder was confirmed in three (25%) probands. The median age of the disease onset in APC-negative patients was somewhere between the mean age of the disease onset in APC- and MYH-positive polyposis. Extraintestinal signs of the disorder were less frequent in APC-negative than in APC-positive probands. Half of APC- and MYH-negative probands with multiple polyposis developed colon cancer. APC- and MYH-negative patients formed a genetically heterogeneous group.

Mammalian MutY homolog (MYH or MUTYH) protects cells from oxidative DNA damage

MutY DNA glycosylase homologs (MYH or MUTYH) reduce G:C to T:A mutations by removing misincorporated adenines or 2-hydroxyadenines paired with guanine or 8-oxo-7,8-dihydroguanine (8-oxo-G). Mutations in the human MYH (hMYH) gene are associated with the colorectal cancer predisposition syndrome MYH-associated polyposis. To examine the function of MYH in human cells, we regulated MYH gene expression by knockdown or overproduction. MYH knockdown human HeLa cells are more sensitive to the killing effects of H2O2 than the control cells. In addition, hMYH knockdown cells have altered cell morphology, display enhanced susceptibility to apoptosis, and have altered DNA signaling activation in response to oxidative stress. The cell cycle progression of hMYH knockdown cells is also different from that of the control cells following oxidative stress. Moreover, hMYH knockdown cells contain higher levels of 8-oxo-G lesions than the control cells following H2O2 treatment. Although MYH does not directly remove 8-oxo-G, MYH may generate favorable substrates for other repair enzymes. Overexpression of mouse Myh (mMyh) in human mismatch repair defective HCT15 cells makes the cells more resistant to killing and refractory to apoptosis by oxidative stress than the cells transfected with vector. In conclusion, MYH is a vital DNA repair enzyme that protects cells from oxidative DNA damage and is critical for a proper cellular response to DNA damage.

Role of MYH Polymorphisms in Sporadic Colorectal Cancer in China: A Case-control, Population-based Study

Biallelic germline variants of the 8-hydroxyguanine (8-OG) repair gene MYH have been associated with colorectal neoplasms that display somatic G:C?T:A transversions. However, the effect of single germline variants has not been widely studied, prompting the present investigation of monoallelic MYH variants and susceptibility to sporadic colorectal cancer (CRC) in a Chinese population. Between January 2006 and December 2012, 400 cases of sporadic CRC and 600 age- and sex-matched normal blood donors were screened randomly for 7 potentially pathogenic germline MYH exons using genetic testing technology. Variants of heterozygosity at the MYH locus were assessed in both sporadic cancer patients and healthy controls. Univariate and multivariate analyses were performed to determine risk factors for cancer onset. Five monoallelic single nucleotide polymorphisms (SNPs) were identified in the 7 exon regions of MYH, which were detected in 75 (18.75%) of 400 CRC patients as well as 42 (7%) of 600 normal controls. The region of exon 1 proved to be a linked polymorphic region for the first time, a triple linked variant including exon 1-316 G?A, exon 1-292 G?A and intron 1+11 C?T, being identified in 13 CRC patients and 2 normal blood donors. A variant of base replacement, intron 10-2 A?G, was identified in the exon 10 region in 21 cases and 7 controls, while a similar type of variant in the exon 13 region, intron 13+12 C?T, was identified in 8 cases and 6 controls. Not the only but a newly missense variant in the present study, p. V463E (Exon 14+74 T?A), was identified in exon 14 in 6 patients and 1 normal control. In exon 16, nt. 1678-80 del GTT with loss of heterozygosity (LOH) was identified in 27 CRC cases and 26 controls. There was no Y165C in exon 7 or G382D in exon 14, the hot- spot variants which have been reported most frequently in Caucasian studies. After univariate analysis and multivariate analysis, the linked variant in exon 1 region (p=0.002), intron 10-2 A?G (p=0.004) and p. V463E (p=0.036) in the MYH gene were selected as 3 independent risk factors for CRC. According to these results, the linked variant in Exon 1 region, Intron 10-2 A?G of base replacement and p. V463E of missense variant, the 3 heterozygosity variants of MYH gene in a Chinese population, may relate to the susceptibility to sporadic CRC. Lack of the hot-spot variants of Caucasians in the present study may due to the ethnic difference in MYH gene.

Distribution of Histone3 Lysine 4 Trimethylation at T3-Responsive Loci in the Heart During Reversible Changes in Gene Expression

Expression in the adult heart of a number of cardiac genes, including the two genes comprising the cardiac myosin heavy chain locus (Myh), is controlled by thyroid hormone (T3) levels, but there is minimal information concerning the epigenetic status of the genes when their expressions change. We fed mice normal chow or a propyl thio uracil (PTU, an inhibitor of T3 production) diet for 6 weeks, or the PTU diet for 6 weeks followed by normal chow for a further 2 weeks. Heart ventricles from these groups were then used for ChIP-seq analyses with an antibody to H3K4me3, a well-documented epigenetic marker of gene activation. The resulting data show that, at the Myh7 locus, H3K4me3 modifications are induced primarily at 5' transcribed region in parallel with increased expression of beta myosin heavy chain (MHC). At the Myh6 locus, decreases in H3K4me3 modifications occurred at the promoter and 5' transcribed region. Extensive H3K4me3 modifications also occurred at the intergenic region between the two Myh genes, which extended into the 3' transcribed region of Myh7. The PTU-induced changes in H3K4me3 levels are, for the most part, reversible but are not invariably complete. We found full restoration of Myh6 gene expression upon PTU withdrawal; however, the H3K4me3 pattern was only partially restored at Myh6, suggesting that full reexpression of Myh6 does not require that the H3K4me3 modifications return fully to the untreated conditions. Together, our data show that the H3K4me3 modification is an epigenetic marker closely associated with changes in Myh gene expression.

The first mutations in the MYH gene reported in Moroccan colon cancer patients

BackgroundBiallelic germline mutations in the MYH gene cause MYH-associated polyposis (MAP) disease, an autosomal recessive form of inherited colorectal cancer. People with MAP tend to develop attenuated multiple adenomatous colon polyps during their lifetime and will have an increased risk of colorectal cancer. Contrary to familial adenomatous polyposis, the number of adenomas is often lower in MAP (from 5 to 100), and even some patients have recently been reported with no identified adenomas.There have been many investigations into MAP that have been conducted in many different countries. Currently there is limited data on MAP in Morocco, and it is reasonable to think, that the prevalence of this form of genetic predisposition is as high as other autosomal recessive genetic diseases found in countries with high rates of consanguinity.The aim of this study is to examine the frequency of MYH mutations in colorectal cancer and/or attenuated polyposis in Moroccan patients. Patients and methodsThe study population consisted of 62 patients; 52 with colorectal cancer, three of them had attenuated polyposis (2 to 99 adenomatous polyps). 10 other patients were referred to our department for polyposis without colorectal cancer.We carried out DNA analysis in 62 patients to screen for the three recurrent mutations c.494A>G (p.Tyr165Cys), c.1145G>A (p.Gly382Asp) and c.1185_1186dup, p.Glu396GlyfsX43, whereas 40 subjects were screened for germline MYH mutations in the whole coding sequence of the MYH gene by direct DNA sequencing. All these 40 patients, except two, had colorectal cancer without polyposis. ResultsThree patients with colorectal cancer and attenuated polyposis carried biallelic mutations in the MUTYH gene one with the c.494 A>G mutation, one with the c.1105delC mutation, one with the c.1145G>A mutation. One patient with 25 adenomas without colorectal cancer carried the c.1145G>A mutation at a homozygote state and one patient with 3 polyps was heterozygote for the mutation c.1145G>A. No biallelic mutations of MYH gene were detected in colorectal cancer patients and in patients with small number (<5) of polyps without colorectal cancer. ConclusionWe report the first biallelic MYH mutations in four Moroccan patients with clinical criteria of MAP; three of them had colorectal cancer with attenuated polyposis. No MYH mutations were found in colorectal patients without polyposis.Despite the relatively small sample size of the current study, our findings suggest that the MAP is not a frequent cause of colon cancer in Morocco as we had expected, and the molecular analysis of MYH gene should be restricted to patients displaying the classical phenotype of MAP.

Lynch Syndrome and MYH-Associated Polyposis

Individuals with Lynch syndrome have an increased risk for colorectal cancer, endometrial cancer, and other associated cancers such as gastric cancer, ovarian cancer, urothelial cancers, hepatobiliary tract cancer, brain cancer, cancer of the small intestine, pancreatic cancer, and particular skin cancers. Lynch syndrome caused by defects in DNA mismatch repair genes, and diagnostic testing for Lynch syndrome begins with microsatellite instability and immunohistochemical analysis on the tumor specimen followed by germline genetic testing and possibly further studies on the tumor. MYH-associated polyposis syndrome is a recently characterized, autosomal recessive, polyposis syndrome caused by biallelic mutations in the MYH gene. Individuals carrying 2 copies of the mutation have a significantly increased risk of polyposis, colorectal cancer, upper gastrointestinal polyps and additional features commonly seen in familial adenomatous polyposis syndrome. Genetic testing for MYH mutation is complicated by the phenotypic overlap of MYH-associated polyposis with other colorectal cancer syndromes. This study serves to clarify the best testing approach.

Características de los pacientes con poliposis adenomatosa familiar en España. Resultados iniciales del Registro Español de Poliposis Adenomatosa Familiar

Background and objectives Familial adenomatous polyposis is an inherited disorder characterized by the presence of multiple colorectal adenomas (more than 100 in the classic form and between 10 and 100 in the attenuated one), with a high risk of colorectal cancer development. To improve the diagnostic and therapeutic management of these patients, the Spanish Registry of Familial Adenomatous Polyposis was created in 2007.We aimed to evaluate the clinicopathological characteristics of patients with familial adenomatous polyposis in Spain. Patients and methods All patients included in the Registry during one year were evaluated with respect to their demographic, clinical, pathological, and genetic characteristics. Results 243 patients of 156 unrelated families from 15 Spanish centers were included. One hundred thirty patients were male, and the mean age at diagnosis was 40 years. According to the clinical presentation, 127 corresponded to the classic form and 116 to the attenuated one. Colorectal adenoma with high-grade dysplasia was identified in 67 (28%) patients, and colorectal cancer in 42 (17%). Extracolonic manifestations were: duodenal involvement (n=46), gastric involvement (n=44), desmoid tumors (n=24), thyroid cancer (n=8), osteomas (n=6) and brain tumor (n=1). APC and/or MYH gene testing was performed in 140 (90%) families, detecting the causative mutation in 75 (54%) of them (70 in the APC gene and 5 in the MYH gene). Conclusions During its first year of operability, a large number of patients and families were included in the Registry. The reduced prevalence of colorectal cancer as well as the large proportion of families submitted to gene testing demonstrated a high-quality clinical practice in Spain.

PWE-067 Recessively inherited non-polyposis colorectal cancer: genotype and phenotype

Introduction Patients diagnosed before 50 years of age have a likely strong genetic or environmental aetiological factor. There is good evidence from population studies1 that recessive inheritance is common in young colorectal cancer patients. Methods A cohort of 133 colorectal cancer patients without multiple polyps or a family history of dominant inheritance were diagnosed under the age of 50 years. They were identified and recruited from the Bobby Moore database in the Family Cancer Clinic, St Mark9s Hospital, Harrow. MYH was screened for germline mutations. As these patients fulfilled Bethesda criteria they were tested for hereditary non-polyposis colorectal cancer (HNPCC) by microsatellite instability analysis and immunohistochemistry of mismatch repair proteins. Immunohistochemistry was also performed on β-catenin and P53. Loss of heterozygosity of the APC locus at 5q21–22 was tested using a set of microsatellite markers. Sequencing was used to identify somatic mutations in KRAS and BRAF. Results Forty-four patients (33%) had cancers proximal to the splenic flexure, 79 (59%) distal and had 11 (8%) synchronous colorectal cancers. Thirty-seven patients (28%) had an affected sibling and 33 (25%) patients had a second-degree relative with cancer at any site. The median age of diagnosis of colorectal cancer was 39 years (range 14–49 years of age). Twenty-six patients (20%) were found to harbour sequence variation in the MYH gene but none of these variants were likely to be pathogenic, and there was no difference in the frequency of these compared to a control group of 50 patients. Eighty percent of tumours were found to be microsatellite stable. 20/30 cancers had nuclear localisation of β-catenin and 21/30 had nuclear localisation of P53 antibodies on immunohistochemistry. Loss of heterozygosity of the APC locus at 5q21–22 was present in 14/30 cases. Thus Wnt pathway activation is likely by over half of this group of cancers. Four cancers had BRAF V600E mutations and five had KRAS codon 12 or 13 mutations. Conclusion In a cohort of 133 young colorectal cancer patients without multiple polyps, most tumours demonstrated Wnt pathway activation and other somatic changes consistent with the classical adenoma-to-carcinoma sequence. Germline mutations in the colorectal neoplasia predisposition gene MYH appear to be rare events in such patients. The majority of recessive inheritance in young patients is probably caused by mutations in unknown predisposition genes.

Aggressive gastric cancer in a patient with an APC mutation and a monoallelic MYH mutation

Familial Adenomatous Polyposis Syndrome (FAP) is an autosomal dominant inherited hereditary colorectal cancer syndrome that is characterized by hundreds to thousands of adenomatous colonic polyps and, without treatment and close surveillance, confers a high lifetime risk of colon cancer. Polyps usually develop in adolescence and virtually all will develop polyps by age 30. It is caused by a mutation in the Adenomatous Polyposis coli (APC) gene which is responsible for tumor suppression and controls apoptosis. While benign fundic gland polyps are common, gastric cancer is rare in the Western population. MYH Associated Polyposis Syndrome (MAP) is an autosomal recessive disease caused by biallelic mutations in the MYH gene which is part of the base excision repair system. Patients with MAP exhibit an attenuated form of polyposis with 10's to 100's of adenomatous polyps and have a later age of onset, typically 10 years later than FAP. Currently to be diagnosed with MAP patients must carry biallelic mutations though recent studies have described similar colon cancer risks for monoallelic carriers. We report on a case of a 65 year old woman with an APC mutation positive FAP (de novo) who also carries a monoallelic mutation in the MYH gene G382D that developed metastatic gastric cancer within a year of a clear CT scan. She had undergone a colectomy with IRA in her 20's and had been followed by yearly endoscopic surveillance that demonstrated polyps in the remaining rectum as well as adenomatous duodenal polyps and gastric polyps with no evidence of malignancy. At 61 she was converted to a I-Pouch and continued with appropriate surveillance. At age 64 Spieglman Stage III duodenal adenomatosis was detected and EGDs were done every 3 months. In March 2008 she presented to the ER with epigastric pain, hematochezia and hemetemesis following an EGD and polypectomy earlier that day. A CT of the chest, abdomen and pelvis did not reveal any abnormalities. She continued to be monitored every 3 months and in March 2009 she had progressed to Spieglman Stage IV. Biopsies were obtained from the duodenal adenomas and were negative for high grade dysplasia. Two months later a CT scan revealed abnormal nodules in the liver. A diagnosis of metastatic gastric cancer was made following further studies.

Identifying Mutations for MYH‐Associated Polyposis

Polyposis associated with mutations in the gene MYH is an autosomal recessive syndrome characterized by the development of colorectal adenomas and cancer. Two common mutations, p.Tyr165Cys (exon 7) and p.Glu382Asp (exon 13), have been shown to account for the majority of the mutations occurring in individuals of Caucasian ancestry. Other mutations have been found throughout the gene and many have been shown to have very low frequencies. Ethnic differences in the mutation spectrum have also been observed. Thus, in order to achieve the highest clinical sensitivity, it is necessary to perform whole-gene sequencing of the MYH gene. The sequencing protocol described allows one to identify mutations throughout the MYH gene.