Identification of a novel BMPR1A germline mutation in a Korean juvenile polyposis patient without SMAD4 mutation

Juvenile polyposis (JP) is characterized by the development of multiple hamartomatous polyps and is inherited as an autosomal dominant trait. Germline mutations of the SMAD4 gene have been reported in JP. We have previously identified three SMAD4 germline mutations in five Korean JP patients. Recently, germline mutations of the BMPR1A (ALK3) gene were reported in JP cases without SMAD4 mutations. In order to determine whether BMPR1A could be involved in the development of JP, we screened all five patients using denaturing high-performance liquid chromatography (DHPLC) analysis. We found that one patient had a BMPR1A germline mutation without a SMAD4 mutation. This patient harbored a novel missense mutation (M470T) in exon 10. After close clinico-pathological examination, one patient who was previously diagnosed to have JP was excluded from the JP group. In total, all four Korean JP patients had either the SMAD4 or the BMPR1A mutation, with three having SMAD4 germline mutations and one carrying a BMPR1A germline mutation.     

SMAD genes in juvenile polyposis.

Juvenile polyposis (JP) is a dominantly inherited condition characterized by the development of multiple hamartomatous tumors, juvenile polyps, in the gastrointestinal tract. The aim of this study was to clarify the role of SMAD4 in JP. DNA from four unrelated JP kindreds and three sporadic JP cases was available for mutation screening. Two truncating defects (one in a familial and one in a sporadic case) and one missense change (in a familial case) that was absent in 55 control samples were detected. To study the possibility that germline mutations in other genes encoding different components of the TGF-beta signaling pathway may be present in these JP patients, mutation analyses of the SMAD2, SMAD3, and SMAD7 genes were also performed. No mutations of these genes were detected in any of the patients. Our results confirm that SMAD4 is a gene predisposing to JP and suggest the existence of further JP loci other than the SMAD2, SMAD3, or SMAD7 genes. Genes Chromosomes Cancer 26:54-61, 1999.     

The rate of germline mutations and large deletions of SMAD4 and BMPR1A in juvenile polyposis

Juvenile polyposis (JPS) is an autosomal dominant syndrome that predisposes individuals to develop gastrointestinal polyps and cancer. Germline point mutations in SMAD4 and BMPR1A have been identified as causing JPS in approximately 40–60% of patients, but few studies have looked at the rate of large deletions. In this study, we determined the overall prevalence of genetic changes of SMAD4 and BMPR1A by sequencing and by screening for larger deletions. DNA was extracted from 102 JPS probands, and each exon and intron–exon boundary of SMAD4 and BMPR1A were sequenced. Coding and non-coding exons of SMAD4 and BMPR1A were screened for deletions with multiplex ligation-dependent probe amplification (MLPA). By sequencing, 20 probands had point mutations of SMAD4 and 22 of BMPR1A . By MLPA, one proband had deletion of most of SMAD4 , one of both BMPR1A and PTEN , one of the 5' end of BMPR1A , and another of the 5' end of SMAD4 . The overall prevalence of SMAD4 and BMPR1A point mutations and deletions in JPS was 45% in the largest series of patients to date. Large deletions are less frequent in JPS patients, but represent other heritable causes of JPS, which should be screened for in pre-symptomatic genetic testing.     

Vessels' morphology in SMAD4 and BMPR1A-related juvenile polyposis

Juvenile polyposis syndrome is a hamartomatous intestinal polyposis associated with malignant changes in 20% of patients at an early age. Germline mutations mostly involve two genes, SMAD4 and BMPR1, with no strong evidence of phenotype-genotype correlation, which could be predictive of the specific long-term evolution. In contrast, PTEN mutations are more commonly associated with Cowden and related diseases. Forty-two unrelated patients affected by juvenile polyposis syndrome were analyzed for germline alterations in the BMPR1A and SMAD4 genes, and for clinical and histological features. Deleterious mutations were found in 14/42 (33%) patients: 5 in BMPR1A and 9 in SMAD4. Low-grade adenomas were present in both SMAD4 and BMPR1A mutation carriers; only patients with SMAD4 mutations harbored carcinoma lesions (5/9). Malformative vessels were present in all SMAD4 related polyps when the mutation involved codons prior to position 423. No gastric polyps were observed in BMPR1A mutation carriers. SMAD4 germline mutations are responsible for a more aggressive digestive phenotype in patients with juvenile polyposis. The presence of malformative vessels within the stromal component might be a useful tool to drive the subsequent genetic and clinical management.     

Thoracic aortic disease in two patients with juvenile polyposis syndrome and SMAD4 mutations

Dilation or aneurysm of the ascending aorta can progress to acute aortic dissection (Thoracic Aortic Aneurysms and Aortic Dissections, TAAD). Mutations in genes encoding TGF‐β‐related proteins (TGFBR1, TGFBR2, FBN1, and SMAD3) cause syndromic and inherited TAAD. SMAD4 mutations are associated with juvenile polyposis syndrome (JPS) and a combined JPS–hereditary hemorrhagic telangiectasia (HHT) known as JPS–HHT. A family with JPS–HHT was reported to have aortic root dilation and mitral valve abnormalities. We report on two patients with JPS–HHT with SMAD4 mutations associated with thoracic aortic disease. The first patient, an 11‐year‐old boy without Marfan syndrome features, had JPS and an apparently de novo SMAD4 mutation (c.1340_1367dup28). Echocardiography showed mild dilation of the aortic annulus and aortic root, and mild dilation of the sinotubular junction and ascending aorta. Computed tomography confirmed aortic dilation and showed small pulmonary arteriovenous malformations (PAVM). The second patient, a 34‐year‐old woman with colonic polyposis, HHT, and features of Marfan syndrome, had a SMAD4 mutation (c.1245_1248delCAGA). Echocardiography showed mild aortic root dilation. She also had PAVM and hepatic focal nodular hyperplasia. Her family history was significant for polyposis, HHT, thoracic aortic aneurysm, and dissection and skeletal features of Marfan syndrome in her father. These two cases confirm the association of thoracic aortic disease with JPS–HHT resulting from SMAD4 mutations. We propose that the thoracic aorta should be screened in patients with SMAD4 mutations to prevent untimely death from dissection. This report also confirms that SMAD4 mutations predispose to TAAD. © 2012 Wiley Periodicals, Inc.     

Comprehensive analysis of SMAD4 mutations and protein expression in juvenile polyposis: evidence for a distinct genetic pathway and polyp morphology in SMAD4 mutation carriers

Juvenile polyposis syndrome (JPS; OMIM 174900) is a rare disorder which is characterized by the presence of hamartomatous polyps throughout the gastrointestinal tract and an increased risk of gastrointestinal malignancy. Mutations of the SMAD4 gene on chromosome 18q21.1 have been shown to cause a subset of JPS cases, with estimates ranging from 20% to >50%. Characterization of the genes that cause the remainder of JPS cases relies on the certainty that SMAD4 is not the causative gene. We have undertaken a comprehensive analysis of germline SMAD4 mutations in a cohort of JPS patients to define the spectrum of mutations that cause JPS. We have analyzed a series of polyps from these patients for SMAD4 protein expression. We have also performed a blinded assessment of polyp material to look for morphological differences between polyps from patients with and without a germline SMAD4 mutation. The results indicate that almost all germline SMAD4 mutations are readily detectable by screening genomic DNA using polymerase chain reaction-based methods; SMAD4 can be excluded as the causative gene in the majority of our JPS cohort. Loss of SMAD4 expression occurs in most polyps from SMAD4 mutation carriers, even those with missense germline mutations. SMAD4 loss in polyps is, however, not a feature of cases that are not caused by SMAD4 mutations, indicating that these polyps develop along a SMAD4-independent pathway. The morphology of polyps from SMAD4 mutation carriers is subtly different from other JPS polyps, notably including a more prominent epithelial component in the former.     

Ganglioneuromatous proliferation associated with juvenile polyposis coli

A case of nonfamilial juvenile polyposis coli was associated ganglioneuromatous proliferation in the polyps is described. The ganglioneuromatous proliferation was characterized by clusters of mature ganglion cells and nerve fiber bundles in the lamina propria and submucosa of the juvenile polyps. The patient had no history of von Recklinghausen's disease or multiple endocrine neoplasia syndrome, type 2b. The implications of this peculiar finding are discussed and the literature is reviewed.     

Somatic alterations in juvenile polyps from BMPR1A and SMAD4 mutation carriers

Juvenile polyposis syndrome (JPS) is a rare autosomal dominant disorder predisposing to gastrointestinal hamartomatous polyps and cancer with a pathogenic SMAD4 or BMPR1A germline mutation (1st‐hit) being identified in about 40–50% of patients. Little is known, however, about the occurrence and nature of somatic alterations (2nd‐hit) in SMAD4‐/BMPR1A‐related juvenile polyps. In this study, we screened 25 polyps from three patients carrying either a pathogenic SMAD4 (c.1244‐1247delACAG) or BMPR1A (c.583C>T; p.Gln195*) germline mutation for somatic alterations. The SMAD4‐related polyps were also analyzed for SMAD4 protein expression by immunohistochemistry. Despite comprehensive screening for loss of heterozygosity (LOH), mutations in the coding sequence, chromosomal rearrangements, and promoter methylation, no somatic alterations could be identified in 14 SMAD4‐related polyps. SMAD4 protein expression, however, was lost in 8 (57%) of 14 juvenile polyps with 6 showing concomitant loss in both, the epithelial and stromal, compartments. In the BMPR1A‐related polyps, five out of nine (56%) displayed LOH. Further analysis of selected polyps revealed that LOH was gene copy number neutral and had occurred in the epithelial compartment. The heterogeneity of genetic mutations and protein expression levels indicates that different modes of gene inactivation can be operational in SMAD4 ‐ and BMPR1A‐related polyp formation. Our observation, that about half of BMPR1A‐related polyps displayed LOH, predominantly in the epithelial compartment, is compatible with BMPR1A acting as a tumour suppressor gene. Still, it remains to be determined whether juvenile polyp development generally requires loss of BMPR1A expression or, as observed in some SMAD4‐related polyps, can occur despite normal protein expression. © 2015 Wiley Periodicals, Inc.     

Frequent 4-bp deletion in exon 9 of the SMAD4/MADH4 gene in familial juvenile polyposis patients.

Familial juvenile polyposis (FJP) is a hamartomatous polyposis syndrome characterized by the appearance of juvenile polyps in the gastrointestinal tract. Patients with this syndrome are at an increased risk for cancer of the colon, stomach, and pancreas. Recently, germline mutations in the SMAD4/DPC4 gene (official symbol MADH4) have been found in the majority of patients suffering from FJP. We have examined 11 unrelated patients with FJP for MADH4 germline mutations by direct sequencing of genomic DNA encompassing all 11 exons of the gene. Besides a novel mutation (959-960delAC at codon 277, exon 6) in one patient, we observed a 4-bp deletion (1372-1375delACAG) in exon 9 in two unrelated patients. Examination with microsatellite markers flanking MADH4 supports an independent origin of the mutation in these two families. The same 4-bp deletion in exon 9 has previously been described in three out of nine patients examined for MADH4 mutations. Our results combined with these previous data demonstrate that a unique 4-bp deletion in exon 9 of MADH4 accounts for about 25% of all FJP cases and that other MADH4 mutations occur in an additional 15% of patients. Genes Chromosomes Cancer 25:403-406, 1999.     

Mutations in DPC4 (SMAD4) cause juvenile polyposis syndrome, but only account for a minority of cases

Juvenile polyps are present in a number of Mendelian disorders, sometimes in association only with gastrointestinal cancer [juvenile polyposis syndrome (JPS)] and sometimes as part of known syndromes (Cowden, Gorlin and Banayan-Zonana) in association with developmental abnormalities, dysmorphic features or extra-intestinal tumours. Recently, a gene for JPS was mapped to 18q21.1 and the candidate gene DPC4 (SMAD4) was shown to carry frameshift mutations in some JPS families. We have analysed eight JPS families for linkage to DPC4. Overall, there was no evidence for linkage to DPC4; linkage could be excluded in two of the eight pedigrees and was unlikely in two others. We then tested these eight families and a further 13 familial and sporadic JPS cases for germline mutations in DPC4. Just one germline DPC4 mutation was found (in a familial JPS patient from a pedigree unsuitable for linkage analysis). Like all three previously reported germline mutations, this variant occurred towards the C-terminus of the DPC4 protein. However, our patient's mutation is a missense change (R361C); somatic missense mutations in DPC4 have been reported previously in tumours. We therefore confirm DPC4 as a cause of JPS, but show that there is considerable remaining, uncharacterized genetic heterogeneity in this disease.      

Hypertrophic and polypoid gastropathy associated with juvenile adenomatous polyposis coli

Juvenile Polyposis is a syndrome with gastrointestinal polyps and increased cancer risk. The commonest form of this syndrome is inherited as autosomal dominant trait and presents as Familial Juvenile Polyposis Coli. Another variant involves mainly the stomach and another is generalized throughout the gastrointestinal tract. We present the case of two brothers with polyposis coli complicated by colonic cancer. The polyps were of juvenile, adenomatous and mixed types. The two patients after a decade of colonic endoscopic polypectomies presented gastric involvement by polyps and needed multiple endoscopic gastric resections. One brother underwent total gastrectomy. This stomach showed diffuse polyposis of hyperplastic and fundic gland types within an unexpected background of foveolar and glandular hypertrophic gastropathy. The patients at present are followed up with endoscopic procedures.     

家族性腺瘤性息肉病家系中一种新的APC基因的胚系突变

目的研究1个家族性腺瘤性息肉病家系的腺瘤样息肉病基因（adenomatous polyposis coli，APC）的胚系突变。方法经结肠镜、组织病理学检查和家族史的调查，确定了1例家族性腺瘤性息肉病（familial adenomatous polyposis，FAP）患者。应用多重连接依赖性探针扩增（multiplex ligation-dependent probe amplification，MLPA）、变性高效液相色谱（denaturing high-performance liquid chromatography，DHPLC）测序等技术对这一家系的成员进行系统的APC全基因筛查。结果在此家系中发现一个新的APC基因的胚系突变c。1999 C〉T（Q667X），这一突变造成了APC基因终止密码子的形成，从而形成有功能障碍的截短蛋白。临床上，此突变可引起严重的FAP症状，早发结直肠腺瘤和腺癌。结论Q667X胚系突变是引起该家系临床表型的原因，受累成员可考虑大肠预防性切除手术。     

APC mutation associated with late onset of familial adenomatous polyposis.

Familial adenomatous polyposis is an autosomal dominantly inherited disorder. Mutation studies in the corresponding gene (APC) may provide information for predictive tests for persons at risk in affected families. We report here a new mutation in exon 6 (codon 233) of the APC gene and clinical data in a large family with late onset of the disease in most affected persons.