Germline mutations of the PTEN/MMAC1 gene in Japanese patients with Cowden disease

PTEN gene mutations in patients with macrocephaly and classic autism: A systematic review

Background: Autism Spectrum Disorder (ASD) is a neurological disorder characterized by massive damage in various fields of development. Impaired social interaction and communication skills, unusual behavior or interests, and repetitive activities are considerably disabling in these patients. There are several challenges in diagnosis of ASD patients such as co-existing epilepsy, difference in clinician attitudes and possibly multifactorial etiology of autistic behavior among children and adults. Research in recent years has emphasized a possible connection between mutations in PTEN and macrocephaly (head circumference > 97th centile). Methods: Articles in English Language were searched from international databases including Medline (PubMed), Google Scholar, Scopus, and CINHAL from January 1998 to January 2016. Results: The results showed that among 2940 patients with behavioral disorders, 2755 individuals had ASD, and 35 cases with macrocephaly had mutations in PTEN. About 77% of the articles (7/9) analyzed mutations in PTEN in patients with head circumference more than 2SD away from the mean, but did not check mutations in this gene in other ASD patients without macrocephaly. To the best of our knowledge, this study is the first systematic review on human PTEN mutations and classical autistic behavior. Conclusion: We conclude that the presence of macrocephaly may not be sufficient to examine the PTEN mutation in this group; however, surveying this gene in all cases of macrocephaly seems to be necessary.

A novel mutation of the PTEN gene in a Japanese patient with Cowden syndrome and bilateral breast cancer

Cowden syndrome (CS), also known as multiple hamartoma syndrome, is an autosomal dominant cancer syndrome associated with a high risk of breast and thyroid cancers. The phosphatase and tensin homolog gene (PTEN) encodes a lipid phosphatase that contains a PTPase domain and a C2 domain and plays a role as a tumor suppressor that negatively regulates the cell-survival signaling pathway initiated by phosphatidylinositol 3-kinase (PI3K). PTEN inhibits angiogenesis, and germline mutations of the PTEN gene are associated with CS. We screened for mutations in the PTEN gene in two unrelated Japanese patients with CS. In one patient, who suffered from bilateral breast cancer, thyroid adenoma, and gastric malignant lymphoma, we found a single-base substitution in exon 2 (115G>C) of the PTEN gene. This transversion results in a germline missense mutation (A39P). To date, nine different mutations have been identified in exon 2 of the PTEN gene in patients with CS and variant CS; however, the A39P missense mutation has not been reported previously. We also detected a previously reported nonsense mutation, 697C>T, resulting in R233X.

Two novel mutations ofPTEN gene in Japanese patients with Cowden syndrome

Cowden syndrome (CS), also known as multiple hamartoma syndrome, is an autosomal dominant cancer syndrome associated with high risk of breast and thyroid cancer. In three unrelated Japanese CS patients, three PTEN germline mutations were identified, including two novel ones: 589A --> T, resulting in Lys197Stop, and 219-222delAAGA. We also detected a previously reported mutation: 697C --> T, resulting in Arg233Stop. Reports from Western countries have indicated that approximately two-thirds of mutations are found in exons 5, 7, and 8, which is almost the same frequency as found in Japanese CS. No genotype-phenotype correlations have been found in CS patients from 21 Japanese families.

Rapid mutation scanning of genes associated with familial cancer syndromes using denaturing high-performance liquid chromatography

Germline mutations in tumor suppressor genes, or less frequently oncogenes, have been identified in up to 19 familial cancer syndromes including Li-Fraumeni syndrome, familial paraganglioma, familial adenomatous polyposis coli and breast and ovarian cancers. Multiple genes have been associated with some syndromes as approximately 26 genes have been linked to the development of these familial cancers. With this increased knowledge of the molecular determinants of familial cancer comes an equal expectation for efficient genetic screening programs. We have trialled denaturing high-performance liquid chromatography (dHPLC) as a tool for rapid germline mutation scanning of genes implicated in three familial cancer syndromes -- Cowden syndrome (PTEN mutation), multiple endocrine neoplasia type 2 (RET mutation) and von Hippel-Lindau disease (VHL mutation). Thirty-two mutations, including 21 in PTEN, 9 in RET plus a polymorphism, and 2 in VHL, were analyzed using the WAVE DNA fragment analysis system with 100% detection efficiency. In the case of the tumor suppressor gene PTEN, mutations were scattered along most of the gene. However, mutations in the RET proto-oncogene associated with multiple endocrine neoplasia type 2 were limited to specific clusters or "hot spots." The use of GC-clamped primers to scan for mutations scattered along PTEN exons was shown to greatly enhance the sensitivity of detection of mutant hetero- and homoduplex peaks at a single denaturation temperature compared to fragments generated using non--GC-clamped primers. Thus, when scanning tumor suppressor genes for germline mutation using dHPLC, the incorporation of appropriate GC-clamped primers will likely increase the efficiency of mutation detection.

Mutations of the human PTEN gene

PTEN (phosphatase and tensin homolog deleted on chromosome ten), a recently discovered tumor suppressor gene, appears to negatively control the phosphoinositide 3-kinase signaling pathway for regulation of cell proliferation and cell survival by dephosphorylating the phosphatidylinositol 3,4,5-triphosphate. To date, 110 germline PTEN mutations have been reported in patients affected with two tumor predisposing syndromes, each having overlapping clinical features: Cowden disease and Bannayan-Riley-Ruvalcaba syndrome. These germline mutations are scattered along the length of the gene, with the exception of exon 9 (no mutation reported) and exon 1 (only two mutations reported). A mutational hot spot is found in exon 5, which encodes the phosphatase catalytic core motif, and recurrent mutations are also found at CpG dinucleotides suggesting deamination-induced mutations. PTEN has also been found to be defective in a large number of sporadic human tumors. In this article, 332 somatic point mutations of PTEN, occurring in primary tumors or metastasis, have been reviewed. Somatic PTEN mutations are more particularly involved in two types of human cancers: endometrial carcinomas and glioblastomas. In most cases, these somatic mutations result in protein inactivation and, as with germline mutations, recurrent somatic mutations are found in CpG dinucleotides. A mutagenesis by insertion-deletion in repetitive elements is however specifically observed in endometrial carcinomas.

Mutation analysis of the PTEN / MMAC1 gene in Japanese patients with Cowden disease

Cowden disease (CD), also known as multiple hamartoma syndrome, is an autosomal dominant cancer syndrome associated with high risk of breast and thyroid cancer. Recently, germline mutations in PTEN / MMAC1, which has nine exons encoding a dual specificity phosphatase with homology to tensin and auxilin, have been identified on chromosome 10q23 in some 40 to 80% of CD patients. Our polymerase chain reaction amplification and sequence analysis of all coding regions identified five different mutations including four novel germline mutations among 5 of 12 unrelated Japanese CD patients. The novel findings included a missense mutation (G --> T) at nucleotide 1004 in exon 8 resulting in an arginine-to-leucine change at codon 335 (R335L), two novel splice-site mutations (209 + 1delGT and 209 + 1delGTAA) in intron 3, and insertion of G at nucleotide 632 in exon 6 (632insG). We also detected a nonsense mutation (C --> T) at nucleotide 697 producing R233X in exon 7, which has been reported previously. From reported phenotypic data concerning CD patients from five different families who had the R233X mutation, it may be suggested that R233X mutation correlates with macrocephaly. Although previous reports have implicated exon 5 as a "hot spot," we found no mutation in exon 5.

A novel PTEN mutation in a Japanese patient with Cowden disease

Cowden disease (CD) is an autosomal dominant syndrome characterized by multiple hamartomatous lesions and an increased risk for malignancies. Recent evidence has indicated that the PTEN gene, encoding a protein tyrosine phosphatase, is the CD susceptibility gene. However, another line of evidence has suggested that CD might be genetically heterogeneous. Clinical features of CD are variable, and there are interfamilial differences in the expression of skin lesions. Therefore, information on PTEN mutations in CD patients should be accumulated to clarify the genotype-phenotype correlation. In the present study, we found heterozygous germline mutations of PTEN in all of three Japanese patients with CD examined, indicating no genetic heterogeneity among our patients. The mutations included two non-sense mutations of R335X and R130X, and a mis-sense mutation of C136R. To the best of our knowledge, the C136R mutation has not previously been reported in CD patients. This novel mutation was located outside the core motif of the phosphatase domain of PTEN protein, where most of the missense mutations previously reported in CD patients were clustered. Mucocutaneous manifestations were far fewer in the patient with this mutation than in the patients with nonsense mutations. Whether the phenotypic difference in mucocutaneous features was due to the different mutations remains unclear.

Somatic mutations and genetic polymorphisms of the PPP1R3 gene in patients with several types of cancers

Recently, we found nonsense and missense mutations of the PPP1R3 (protein phosphatase 1, regulatory subunit 3) gene in diverse human cancer cell lines and primary lung carcinomas, indicating that PPP1R3 functions as a tumor suppressor in human carcinogenesis. In this study, to assess the prevalence of PPP1R3 mutations in human primary cancers and the genetic diversity of the PPP1R3 gene in the human population, somatic mutations and genetic polymorphisms in the PPP1R3 gene were examined in 137 pairs of cancerous and non-cancerous tissues of patients with cancers of colon, ovary, and liver. Five somatic mutations including two missense mutations were detected in three cancerous tissues consisting of two colorectal carcinomas and one ovarian carcinoma. Five novel single nucleotide polymorphisms (SNPs) associated with the substitution of amino acids were also identified in cancer patients, in addition to five known nonsynonymous SNPs, including three previously reported ones as having an impact on the susceptibility to insulin resistant disorders. Differences in the activities and properties of multiple PPP1R3 proteins, which are produced in human cells due to variable somatic mutations and genetic polymorphisms in the PPP1R3 gene, can be involved in human carcinogenesis and susceptibility to diseases.