Mariapina Montera

A silent mutation in exon 14 of the APC gene is associated with exon skipping in a FAP family

Editor—Familial adenomatous polyposis (FAP) is an autosomal dominantly inherited disorder characterised by the development of hundreds to thousands of adenomatous polyps in the colon and rectum. If left untreated, there is a very high risk of colorectal cancer. Adenomatous polyps may also develop proximally in the stomach and the distal part of the duodenum. FAP is also associated with a variety of extracolonic benign and malignant manifestations, including congenital hypertrophy of the retinal pigment epithelium (CHRPE), dental abnormalities, desmoid tumours, osteomas, epidermoid cysts, hepatoblastoma, and thyroid neoplasia.1 Germline mutations of the APC gene localised on chromosome 5q21.22 are responsible for FAP.2 3 APC is a tumour suppressor gene encoding a 2843 amino acid protein, which contains multiple functional domains and which mediates growth regulatory signals by its association with a variety of cytoplasmic proteins. More than 300 different APC mutations have so far been identified distributed throughout the whole gene, with a higher concentration in the 5′ part of exon 15 (codons 713-1597).4 5 The majority of mutations are predicted to introduce premature termination signals resulting from single nucleotide alterations, small insertions or deletions, or splice site mutations that lead to truncation of the normal protein product.4 Missense mutations have rarely been reported and their functional implications are often unclear.6 7 Larger deletions and insertions have been described, as well as genomic rearrangements resulting from recombinations mediated by Alu elements which cause inappropriate exon splicing.8-10 Isoforms of APC transcripts lacking exon 9, exon 10A, and exon 14 encoded sequences have been reported.2 11-13 Isoforms lacking exon 9 or exon 14 owing to splice site mutations have also been associated with a FAP phenotype.14-17 In this study, we describe a G→T transversion at nucleotide position 1869 in exon 14 which gives …

Prevalence of the E1317Q Variant of the APC Gene in Italian Patients with Colorectal Adenomas

Loss of APC is an initial, rate-limiting event in inherited and sporadic colorectal tumorigenesis. Rare germline APC mutations have been identified in patients with multiple colorectal adenomas. Recently, the E1317Q APC variant has been associated with a predisposition to the development of multiple colorectal adenomas. In this study, the prevalence of the E1317Q variant was examined in 182 patients with single or multiple colorectal adenomas, and in 235 controls. In all, E1317Q was identified in two of 182 patients with adenomatous polyps (1.1%) and in two of 235 controls (0.8%) (p = 0.59). The risk of harboring adenoma(s) among subjects bearing the E1317Q variant was 1.29 (95% CI 0.09-18.0). No difference in the prevalence of E1317Q between cases with single (2.0%) or multiple colorectal adenomas (0.7%) and controls (0.8%) was found. None of the subjects with a family history of colorectal cancer carried the E1317Q variant. In conclusion, our results confirm that only a very small fraction of colorectal adenomas may be associated with the presence of E1317Q.

Granular cell tumor in a PHTS patient with a novel germline PTEN mutation

The autosomal dominant inherited syndromes known as Cowden syndrome (CS,MIM158350) andBannayanRuvalcaba-Riley syndrome (BRR, MIM 153480) share clinical characteristics suchashamartomatouspolyps of the gastrointestinal tract, mucocutaneous lesions, and increased risk of developing neoplasms [Eng and Ji, 1998]. Recently, CS and BBR have been indicated as PTEN hamartoma tumor syndrome (PHTS) [Marsh et al., 1999]. CS and BRR are in fact allelic variants of a single genetic entity associated to germline mutations in phosphatase and tensin homolog deleted on chromosome 10 gene (PTEN/MMAC1/TEP1) [Liaw et al., 1997; Marsh et al., 1997]. Granular cell tumor (GCT), also known as granular cell schwannoma, is an uncommon lesion of neural origin characterized by PAS-positive eosinophilic granular cells, which are immunoreactive for S-100 protein and ultrastructurally contain large numbers of secondary lysosomes. Electron microscopy shows that secondary lysosomes are composed of membrane remnants [Scheitauer et al., 1999]. Recent data suggest that granular cell formation is not characterized by specific chromosomal imbalance as a distinct tumor entity but rather it is a degenerative process of cells of various origin showing the genetic changes of the underlying tumor [Rickert and Paulus, 2002]. GCT occurs at numerous anatomical sites. Most frequently affected are the skin and the subcutaneous tissue. Approximately 5% of GCT is found in the intestinal tract. We describe here a patient with multiple granular cells tumors, phenotypic findings of PHTS, and anovelPTEN gene germline mutation. The proband, a 38-year-old Caucasian male, the only child of a non-consanguineous couple, was referred for genetic counseling to the hereditary cancer clinic. The family history is not remarkable. Both parents are alive and do not present any clinical symptom or sign. The probandwas in goodhealthup to age 16 years,when he began to suffer from blurred vision; a diagnosis of chorioretinitis wasmade. At the age of 21, he underwent partial resection of the thyroid gland (microfollicular and trabecular adenoma). At the age of 22, a fibrous lesion was removed from the left turbinate, as well as three ‘‘cystic’’ lesions from the left hand (two from the thumb and one from the fifth finger), which were shown to be granular cell tumors (Fig. 1A,B). At 24, acupheni and exophthalmus of the right eye were recorded; two years later, a parasellar angiofibroma, which was thought to have caused an arterio-venous fistula of the cavernous sinus, was removed. At 28, bilateral cataract was diagnosed: the left eye was operated on and the right cataract was removed at 34. At 29, the patient developed dysphagia and gastric pain. Endoscopies revealed diffuse gastro-esophageal polyposis (hyperplastic polyps) and multiple polyps in the rectum and sigma (‘‘edematous mucosa’’). In the same year, three more hand lesions were removed, which were shown to be further granular cell tumors. A further colonoscopy revealed multiple hyperplastic polyps (<100) in the descending colon, sigma, and rectum, one of which was, however, a schwannoma of the intestinal mucosa. A large (3.5 cm) polyp with an ulcerated base in the transverse colon was also present. Histological examination showed this to be a juvenile polyp. Physical examination of the proband showed a bright male, with numerous (>6) facial papular lesions, a occipital-fronto circumference of 63 cm, a left-convex scoliosis, and penile lentigines. The clinical diagnosis was of PHTS although neurofibromatosis was also considered in differential diagnosis. Mutational analysis was performed on genomic DNA prepared from isolated leucocytes using aGFXGenomic Blood Purification Kit (Amersham Pharmacia Biotech Inc., Piscataway, NJ) by single strand conformation polymorphism (SSCP). Genomic DNA was amplified withprimersflanking the exonsofPTEN [Risinger et al., 1997]. SSCP was carried out as described previously [Stella et al., 1994]. The variant conformer was sequenced using an ABI PRISM TM 377 DNA Sequencer Grant sponsor: MURST, Ministero dell’Università e della Ricerca Scientifica e Tecnologica, Cofinanziamento 1998; Grant sponsor: Cofinanziamento MURST, Bando 2001; Grant sponsor: Galliera Genetic Bank, Progetto Telethon C42.

Clinical Findings in a Family with Familial Adenomatous Polyposis and a Missense Mutation of the Adenomatous Polyposis Coli Gene

BACKGROUND More than 100 different mutations in the adenomatous polyposis coli (APC) gene have been identified; virtually all lead to the production of a truncated protein. Clinical details of patients with missense mutations undoubtedly cosegregating with the disease have not been reported and may be relevant in understanding the APC protein function. METHODS In one family with familial adenomatous polyposis (FAP) the APC gene was analyzed by SSCP and sequencing of the aberrant SSCP band. RESULTS A missense mutation in exon 15 at nucleotide 4921 segregating with the disease was observed. This predicts a tryptophan instead of an arginine at amino acid 1641 of the APC protein. No such mutation was present in 100 control subjects. CONCLUSIONS In this family the colonic manifestations are as expected for classical FAP. However, the occurrence of congenital hypertrophy of the retinal pigment epithelium is unusual, owing to the inconsistency of this manifestation between family members and because congenital hypertrophy of the retinal pigment epithelium is generally absent when mutations are after codon 1387.

Expression and Genomic Configuration of GM-CSF, IL-3, M-CSF Receptor (C-FMS), Early Growth Response Gene-1 (EGR-1) and M-CSF Genes in Primary Myelodysplastic Syndromes

Peripheral blood mononuclear cells from seventeen patients with primary myelodysplastic syndromes (MDS) in advanced stage were enriched for blasts and tested for (1) karyotype, (2) genomic configuration and (3) expression of IL-3, GM-CSF, FMS and EGR-1 genes which are all located on the long arm of chromosome 5. The expression of the M-CSF gene, that has been recently reassigned to the short arm of chromosome 1 (lp), was also investigated. Aims of the study were to (1) assess the potential role of the expression of these genes in the maintenance and expansion of the neoplastic clones and (2) search for constitutional losses or rearrangements of one allele followed by a deletion of the second allele of the same genes in the leukemic cells. The latter issue was investigated by comparing, in 8 cases, constitutive DNA from skin fibroblasts with leukemic DNA. Eleven of the 17 patients had abnormal karyotypes. The M-CSF gene was expressed in 6 cases and the FMS and the EGR-1 genes were expressed in 2 of the latter cases. An autocrine mechanism of growth could be hypothesized only for the 2 patients whose cells expressed both the M-CSF and FMS genes. No germline changes or rearrangements were observed in any of the genes studied. Thus, deregulation of genes encoding for certain hemopoietic growth factors or receptors does not seem to represent a major mechanism of MDS progression.

The familial adenomatous polyposis region exhibits many different haplotypes

Abstract In the present study, we used five different polymorphic markers to construct the haplotype at the adenomatous polyposis coli (APC) locus in families with familial adenomatous polyposis (FAP) and in the normal Italian population. Non-ambiguous haplotypes were reconstructed from 246 normal chromosomes and 65 FAP chromosomes. In the control population, the four polymorphisms intragenic to APC gave rise to 16 haplotypes, the most common of which (II and XV) accounted for over 50% of all chromosomes. In FAP patients, 13 haplotypes were found but their distribution was not statistically different from normal subjects. Eighty complete chromosomal haplotypes (many fewer than the theoretical maximum of 208) for the five polymorphic sites assayed were observed in the control population, 35 being found in the FAP patients. We compared the distribution of these haplotypes within the two groups; no statistically significant differences between normal and FAP chromosomes were found. The elevated heterogeneity of FAP chromosomes was clearly confirmed by the observation that 19 patients who carried one or other of the two most common APC mutations (nt 3183 and nt 3927) showed 18 different haplotypes. On the basis of these results, we were not able to identify a founder FAP chromosome. Various mechanisms are presented to explain this observation.

Altered erythropoiesis and decreased number of erythrocytes in children with neuroblastoma

Neuroblastoma (NB) is a pediatric tumor presenting at diagnosis either as localized or metastatic disease, which mainly involves the bone marrow (BM). The physical occupancy of BM space by metastatic NB cells has been held responsible for impairment of BM function. Here, we investigated whether localized or metastatic NB may alter hematopoietic lineages’ maturation and release of mature cells in the periphery, through gene expression profiling, analysis of BM smears, cell blood count and flow cytometry analysis. Gene ontology and disease-associated analysis of the genes significantly under-expressed in BM resident cells from children with localized and metastatic NB, as compared to healthy children, indicated anemia, blood group antigens, and heme and porphyrin biosynthesis as major functional annotation clusters. Accordingly, in children with NB there was a selective impairment of erythrocyte maturation at the ortho-chromic stage that resulted in reduced erythrocyte count in the periphery, regardless of the presence of metastatic cells in the BM. By considering all NB patients, low erythrocyte count at diagnosis associated with worse survival. Moreover, in the subset of metastatic patients, low erythrocyte count, hemoglobin and hematocrit and high red cell distribution width at follow-up also associated with worse outcome. These observations provide an alternative model to the tenet that infiltrating cells inhibit BM functions due to physical occupancy of space and may open a new area of research in NB to understand the mechanism(s) responsible for such selective impairment.