Gene Mutation Sites Research Articles

Differences in the transcriptome of medullary thyroid cancer regarding the status and type of RET gene mutations

Medullary thyroid cancer (MTC) can be caused by germline mutations of the RET proto-oncogene or occurs as a sporadic form. It is well known that RET mutations affecting the cysteine-rich region of the protein (MEN2A-like mutations) are correlated with different phenotypes than those in the kinase domain (MEN2B-like mutations). Our aim was to analyse the whole-gene expression profile of MTC with regard to the type of RET gene mutation and the cancer genetic background (hereditary vs sporadic). We studied 86 MTC samples. We demonstrated that there were no distinct differences in the gene expression profiles of hereditary and sporadic MTCs. This suggests a homogeneous nature of MTC. We also noticed that the site of the RET gene mutation slightly influenced the gene expression profile of MTC. We found a significant association between the localization of RET mutations and the expression of three genes: NNAT (suggested to be a tumour suppressor gene), CDC14B (involved in cell cycle control) and NTRK3 (tyrosine receptor kinase that undergoes rearrangement in papillary thyroid cancer). This study suggests that these genes are significantly deregulated in tumours with MEN2A-like and MEN2B-like mutations; however, further investigations are necessary to demonstrate any clinical impact of these findings.

Generation of biallelic knock-out sheep via gene-editing and somatic cell nuclear transfer.

Transgenic sheep can be used to achieve genetic improvements in breeds and as an important large-animal model for biomedical research. In this study, we generated a TALEN plasmid specific for ovine MSTN and transfected it into fetal fibroblast cells of STH sheep. MSTN biallelic-KO somatic cells were selected as nuclear donor cells for SCNT. In total, cloned embryos were transferred into 37 recipient gilts, 28 (75.7%) becoming pregnant and 15 delivering, resulting in 23 lambs, 12 of which were alive. Mutations in the lambs were verified via sequencing and T7EI assay, and the gene mutation site was consistent with that in the donor cells. Off-target analysis was performed, and no off-target mutations were detected. MSTN KO affected the mRNA expression of MSTN relative genes. The growth curve for the resulting sheep suggested that MSTN KO caused a remarkable increase in body weight compared with those of wild-type sheep. Histological analyses revealed that MSTN KO resulted in muscle fiber hypertrophy. These findings demonstrate the successful generation of MSTN biallelic-KO STH sheep via gene editing in somatic cells using TALEN technology and SCNT. These MSTN mutant sheep developed and grew normally, and exhibited increased body weight and muscle growth.

Mutations of K-ras and v-raf murine sarcoma viral oncogene homolog B1 gene in colorectal cancer and their clinical significance

Objective To investigate mutations of K- ras and v- raf murine sarcoma viral oncogene homolog B1(BRAF) genes in colorectal cancer and their clinical significance. Methods 412 cases of colorectal cancer tissue specimens were selected.Real- time quantitative polymerase chain reaction(Real- time PCR) was used to study the characteristics of K- ras and BRAF gene mutation sites and their relationship with clinicopathologic parameters. Results In 412 cases, the mutation rate of K- ras gene was 37.9%.The K- ras mutation rate in rectal cancer(45.2%) was higher than in colon cancer(28.8%, P< 0.05). The rate of single locus mutation was 35.4%, while the rate of double locus mutation was 2.2% and the rate of triple locus mutation was 0.2%.The K- ras mutation was most commonly located in codons 12 and 13,in which the rate of codon 12 was 32.0%.The mutation patterns of codon 12 included G12D(15.0%), G12V(9.5%), G12C(3.9%), G12S (2.9%), G12A(2.4%) and G12R(0.7%). The mutation pattern of thre codon 13 was G13D (6.1%).G→A was the most common mutation pattern.The K- ras gene mutation rate ofⅠ+Ⅱstage(30.4%) was lower than that ofⅢ+Ⅳstage(45.2%), with statistically significant difference(P< 0.05). Further analysis showed the mutation rate(5.9%)of G12V in TNM stageⅠ+Ⅱwas lower than that in stageⅢ+Ⅳ(13.0%, P< 0.05). The K- ras mutation was irrelevant to gender, age, tumor size, clinical tumor type, histological classification and lymphatic metastasis. The BRAFV600E mutation rate of colorectal cancer was 2.4%, and that of colon cancer(4.9%) was higher than rectal cancer(0.4%), with statistically significant difference(P<0.05). Conclusion In colorectal cancer, single locus mutation is most common in K- ras mutation, in which G12D was the main pattern. The mutation status of the G12V can probably promote the progresssion of colorectal cancer.The K- ras mutation rate in rectal cancer was higher than in colon cancer, while the BRAF mutation rate in colon cancer was higher than in rectal cancer.The mechanisms of K- ras and BRAF mutation in colon and rectal cancers may be different. Key words: K-ras gene; v-raf murine sarcoma viral oncogene homolog B1 gene; Gene mutation; Colorectal caner

Molecular epidemiology analysis of glucose-6-phosphate dehydrogenase gene mutations among infertile patients in Shenzhen

To explore the incidence and genotypes of glucose-6-phosphate dehydrogenase (G6PD) gene mutations among infertile patients in Shenzhen. DNA samples from 851 infertile patients were tested for 25 G6PD gene mutation sites using a multiplex SNaPshot assay. The incidence of G6PD gene mutations among infertile patients in Shenzhen was 17.63%. Male and female abnormal rates were 15.13% and 20.09% respectively. Most of the female abnormal cases were heterozygotes. Mutations involved 11 haplotypes in 10 sites. 1311C> T/IVS-11 93T> C was the most common mutation, accounting for 72.00% (108/150) abnormal cases. Forty three cases of missense mutations were detected, including 19 cases of 1376G> T, 9 cases of 1388G> A, 5 cases of 95A> G and 871G> A/1311C> T/IVS-11 93T> C, 1 case of 202G> A, 835A> T, 1360C> T, 1376G> T and 392G> T/1311C> T/IVS-11 93T> C. The incidence of G6PD gene mutations among infertile patients in Shenzhen was high and the mutation types were various. Therefore, the G6PD deficiency genetic screening should be performed prior to assisted reproduction. This investigated results provided valuable basic data for genetic counseling, preimplantation genetic diagnosis and prenatal diagnosis.

P12 Neurobehavioural disorders in Duchenne muscular dystrophy

Abstract Variable neurobehavioural disorders and IQ one SD below average are recognised comorbidities in Duchenne muscular dystrophy (DMD), reflecting the disrupted expression of different length dystrophin isoforms in the brain, based on the dystrophin gene mutation site. Following a screening of 84 DMD boys with validated questionnaires, we previously reported 15 with severe learning disability and 41 with scores predictive of autistic spectrum disorder (ASD). Attention deficit and hyperactivity disorder (ADHD) traits, conduct and emotional problems were also described. Overall, a higher proportion of boys affected had mutations towards the 3’ end of dystrophin. We performed targeted neuropsychological assessments including: Wechsler Intelligence Children Scale-IV (WISC-IV), Developmental Dimensional and Diagnostic Interview (3Di), Conners-3 Questionnaires, Child Behaviour Checklist (CBCL). We found marked unevenness of performance on the WISC-IV. Eight out of 12 boys had significant difference between verbal comprehension (VCI) and perceptual reasoning (PRI), with VCI more compromised. Eight out of 19 met criteria for ASD on the 3Di. In 5 boys with ASD the CBCL showed higher scores for internalising and externalising difficulties compared to non-ASD. There were associations between lower IQ and autistic social communication difficulties. On the Conners 6/17 boys met criteria for hyperactivity and 7 for inattention problems. There was a strong association between ASD and severe ADHD symptoms of hyperactivity (OR = 22.5) and inattention (OR = 54). There was a trend towards children with mutations towards the 3’ end of the gene, having a greater chance of ASD (OR = 3.4). In our on-going study, neurobehavioural disorders emerged as important facets in DMD, with confirmed ASD prevalence rates much higher than the general population. Whilst further exploring the role of dystrophin in the brain, children with DMD should be provided with neurobehavioural-targeted support.

Evaluation of mutagenic activity in the Nakdong river and advanced drinking water treatment processes

The previously proved method of Ames test was followed to measure the mutagenic activity. We used Salmonella typhimurium which has special gene mutation site with a single compound characteristic and histidine operon, and measured at the four (Gumi, Gangjung, Gachang, Hyunpung) branch points of Nakdong river for one year. We used Standard Methods for general water analysis with the items as water temperature, pH, DO, BOD, COD, KMnO4, T-N, T-P, NH3-N, TOC, and AOX. Hyunpung branch, where the Nakdong and the Gumho river seems to be mixed enough, showed higher mutagenic activity than the other 3 branches. Every point of Nakdong river showed the TA98 mutagenic activity higher than 2, while TA100 was lower than 2. Most of the mutagenic activity was detected from methanol extracts. These results indicate that Nakdong river water quality is getting deteriorated, and that Nakdong river is influencing the mutagenic activity by Frame-shift type mutation and its polar substances. Correlations (R) between mutagenic activity and concentrations of water analysis items as TOC, AOX, BOD, COD, T-N, and T-P, resulted as 0.768, 0.787, 0.743, 0.688, 0.757, 0.628, respectively, and mutagenic activities of TA98 and TA100, after the treatment of ozone and activated carbon, decreased by chlorine pre-treatment. Finally, if the injected concentration of ozone was higher than 1.0 mL, TA98 and TA100 showed lower mutagenic activities than 2.

Analysis of DMD gene mutations in 59 families in northern China

Objective To detect the DMD gene mutation sites and the regions of breakpoints in Duchenne/Becker muscular dystrophy (DMD/BMD) patients in northern China. Methods Multiplex amplifiable probe hybridization (MLPA) was used to detect the mutation in 59 cases (51 cases with DMD and 8 with BMD) from northern China and dystrophin gene mutations in their parents. Results From northern China and dystrophin gene mutations 59 families found gene deletions in 33 cases of 59 DMD/BMD patients (55.9%), duplications in 6 cases (10. 2%) and point mutation in one case (1.7%). Intron 44 was most frequently affected (n = 13, 33.3%), followed by intron 50 (n = 11, 28.2%) and intron 45 (n=8, 20.5%). The novel mutations were identified, in two patients including two independent duplications carried by patient D1 149 and a point mutation [5208del(A)] carried by patient D1 65, which were not included in Leiden database. In addition, an exon 22 deletion was found in one patient, which was the first reported case in Chinese patients. Conclusions Deletions are mostly located in the hotspot between exon 45 and 50. Duplications mostly occurred in the 5' end of the gene. Intron 44 is the most frequently affected breakpoint in northern Chinese population. Key words: Muscular dystrophy, Duchenne/Beckey; Dystrophin; Genes mutation

Development of gene-tagged markers for quantitative trait loci underlying rice yield components

Higher yields of rice have always been a predominant goal in rice breeding techniques. However, the inheritances of rice yield and its components are still unknown, and no information regarding suitable alleles can be directly provided for improving the rice yield level until three major quantitative trait loci (QTLs) have been cloned and functionally characterized. These QTLs contain Gn1a for grain number per panicle and GS3 and GW2 for grain weight. It has been proven that these three genes show a potential in improving the rice yield level. However, the distribution of suitable alleles on these three loci in rice cultivars and germ plasm are yet to be elucidated, this retards the progress of the utilization of suitable alleles in rice breeding techniques to produce higher yields. In the present study, we developed a set of gene-tagged markers based on the gene mutation sites Gn1a-M1 and Gn1a-M2 for Gn1a, GW2-HapI for GW2, and GS3-PstI for GS3. The results demonstrated that these STS markers could clearly differentiate between the different alleles at each gene locus. A survey of the allele distributions of the abovementioned three genes was performed with 156 cultivars. It was observed that the 5150-Gn1a allele was absent on the Gn1a locus and only two type alleles (Ha-Gn1a and Ko-Gn1a) were present, of which 54.3% indica and 21.5% japonica cultivars contained the Ha-Gn1a allele. Two alleles (MH-GS3 and ZS-GS3) were detected on the GS3 locus, and 48.6% indica and 9.9% japonica cultivars harbored the suitable allele MH-GS3. Further, all the cultivars contained the FA-GW2 allele on GW2, whereas the WY-GW2 allele was not found. These results further suggested that some of the alleles residing in the indica subspecies have introgressed into the japonica group with a very low frequency. The gene-tagged markers developed in the present study can be directly used as a tool for marker-aided selection (MAS) in rice breeding techniques to produce higher yields.

Desmoid Tumors in a Dutch Cohort of Patients With Familial Adenomatous Polyposis

Desmoid tumors are a severe extracolonic manifestation in familial adenomatous polyposis (FAP). Identification of risk factors might be helpful in the management of FAP patients with such tumors. The aim of this study was to assess potential risk factors for the development of desmoids in a cohort of Dutch FAP patients. The medical records of 735 FAP patients were analyzed for the occurrence of desmoids. Relative risks and survival times were calculated to assess the influence of potential risk factors (female sex, family history, mutation site, abdominal surgery, and pregnancy) on desmoid development. Desmoid tumors were identified in 66 of the 735 patients (9%). The cumulative risk of developing desmoids was 14%. No correlation was found between specific adenomatous polyposis coli mutation sites and desmoid development. Patients with a positive family history for desmoids had a significant increased risk to develop this tumor (30% vs 6.7%, P < .001). No association was found between female sex or pregnancy and desmoid development. Most desmoid patients (95%) had undergone previous abdominal surgery. In a substantial proportion of patients with an ileorectal anastomosis, it was impossible to convert the ileorectal anastomosis to an ileal pouch-anal anastomosis as a result of desmoid development. A positive family history of desmoids is an evident risk factor for developing desmoids. Most desmoids develop after colectomy. No correlation was found between desmoids and the adenomatous polyposis coli gene mutation site, female sex, and pregnancy. Ileal pouch-anal anastomosis is the appropriate type of surgery in FAP patients with a positive family history for desmoids.

P53 Gene and Protein Status: The Role of p53 Alterations in Predicting Outcome in Patients With Bladder Cancer

The p53 gene status (mutation) and protein alterations (nuclear accumulation detectable by immunohistochemistry; p53 protein status) are associated with bladder cancer progression. Substantial discordance is documented between the p53 protein and gene status, yet no studies have examined the relationship between the gene-protein status and clinical outcome. This study evaluated the clinical relationship of the p53 gene and protein statuses. The complete coding region of the p53 gene was queried using DNA from paraffin-embedded tissues and employing a p53 gene-sequencing chip. We compared p53 gene status, mutation site, and protein status with time to recurrence. The p53 gene and protein statuses show significant concordance, yet 35% of cases showed discordance. Exon 5 mutations demonstrated a wild-type protein status in 18 of 22 samples. Both the p53 gene and protein statuses were significantly associated with stage and clinical outcome. Specific mutation sites were associated with clinical outcome; tumors with exon 5 mutations showed the same outcome as those with the wild-type gene. Combining the p53 gene and protein statuses stratifies patients into three distinct groups, based on recurrence-free intervals: patients showing the best outcome (wild-type gene and unaltered protein), an intermediate outcome (either a mutated gene or an altered protein) and the worst outcome (a mutated gene and an altered protein). We show that evaluation of both the p53 gene and protein statuses provides information in assessing the clinical recurrence risk in bladder cancer and that the specific mutation site may be important in assessing recurrence risk. These findings may substantially impact the assessment of p53 alterations and the management of bladder cancer.

Genotype-Phenotype Correlations as a Guide in the Management of Familial Adenomatous Polyposis

The options for prevention of colorectal cancer in familial adenomatous polyposis are either a colectomy with ileorectal anastomosis (IRA) or a total proctocolectomy with ileal pouch-anal anastomosis (IPAA). Rectal cancer risk is eliminated by IPAA, but complication rate is higher than in IRA. Mutation analysis might predict severity of polyposis and be helpful in the surgical decision. Patients from the Dutch Polyposis Registry with an IRA were subdivided according to the site of adenomatous polyposis coli gene mutation into the attenuated (1), intermediate (2), and severe (3) genotype groups. Cumulative risks of secondary rectal excision and rectal cancer were calculated for each group. A total of 174 patients underwent an IRA: 26 patients from group 1, 121 from group 2, and 27 from group 3. Cumulative risks of rectal cancer 15 years after surgery were 6%, 3%, and 8% in groups 1, 2, and 3, respectively. Cumulative risks of rectal excision 20 years after IRA were 10%, 43%, and 74%, respectively. The risk of rectal excision was significantly higher in group 3 than in the other groups (P < .05). The risk of secondary rectal excision after IRA can be predicted on the basis of the adenomatous polyposis coli mutation site. An IRA appears to be the appropriate treatment in patients with the attenuated genotype. Patients with a severe genotype are good candidates for an IPAA.

Chinese Presenilin-1 V97L mutation enhanced Aβ42 levels in SH-SY5Y neuroblastoma cells

Presenilin-1 gene mutations have been proven to be associated with the majority of early-onset familial Alzheimer's disease (FAD). There have been, however, no systematic studies of Presenilin-1 gene mutation in FAD in China so far. We found a novel Val → Leu missense mutation at codon 97 (Val97Leu) of the Presenilin-1 gene in a Chinese FAD pedigree. To verify whether this mutation is pathologically functional, we established mutation type and wild type Presenilin-1 gene stably transfected cell lines (human neuroblastoma SH-SY5Y cells) to detect β-amyloid (Aβ) concentrations using ELISA and radioimmunity methods. We also examined levels of β-amyloid precursor protein cleaving enzyme (BACE) and amyloid precursor protein (APP) to explore their impact upon β-amyloid production. Our results showed that Aβ42 concentration was significantly enhanced at 48 h when compared to that at 24 h in the mutant type cells. At 48 h Aβ42 levels in the V97L mutants was also found to be elevated significantly, both intracellularly and extracellularly when compared to wild and mock transfected cells. The total Aβ in either group did not alter, consistent with unchanged BACE and APP expression levels. Our data reveal that the Presenilin-1 V97L variant can elevate Aβ42 levels both intracellularly and extracellularly, and was a potentially pathogenic mutation for this Chinese FAD pedigree. It also suggests that there are common mechanisms in the pathogenesis of FAD between Chinese and other ethnic populations, although their gene mutation sites are different.

Recurrent Mutation of the KIF21A Gene in Japanese Patients with Congenital Fibrosis of the Extraocular Muscles

To report recurrent mutation of the KIF21A gene in three Japanese families in which some members have congenital fibrosis of the extraocular muscles type 1 (CFEOM1), and to describe the clinical characteristics of the families. Standard ocular examinations were performed on 18 normal and affected members of three unrelated families. To detect mutations, we determined the DNA sequence of exons 8, 20, and 21 and the splice sites of the KIF21A gene. All affected members had a heterozygous mutation of the KIF21A gene in exon 21 (R954W). Clinically, each patient had congenital bilateral ptosis, an infraducted primary position of each eye, and the inability to raise either eye above midline. The KIF21A gene mutation R954W was detected in the patients with CFEOM1 screened in this study, all of whom were Japanese, reflecting similar reports from Europe, America, the Middle East, and Japan. We suggest that mutations of the KIF21A gene contribute to the development of CFEOM1 regardless of ethnicity. We also found that the delimitation of the KIF21A gene mutation site enabled us to efficiently detect the KIF21A gene mutation despite the large number of KIF21A gene exons.

Rac2 expression and mutation in human brain tumors

Rac1 and Rac2 are interchangeable in NADPH oxidase activation. Rac1 plays an important role in regulating nuclear signalling and in the activation of transcriptional factors that regulate gene expression and cell growth. Our previous study observed mutation in effector region of Rac1 gene in brain tumors. Little is known about the expression and mutation of Rac2 in human brain tumors. We examined the expression of Rac2 by using reverse transcriptase-polymerase chain reaction (RT-PCR) and northern blot analysis and the mutation of Rac2 gene by using DNA sequence analysis. The decreased expression of Rac2 was found in 15 cases (57.7%) including 8 of 10 astrocytomas, 2 of 8 meningiomas, and 5 of 8 pituitary adenomas. Two of 13 cases with decreased expression of Rac2 had gene mutation. Only two of 26 cases had Rac2 overexpression in which no Rac2 gene mutation was found. Four of 8 cases with normal Rac2 expression had Rac2 gene mutation. The site of Rac2 gene mutation had no hot spots and was not concentrated in the effector region. Our results showed a low frequency of mutation and no hot spots of mutation in Rac2 gene in brain tumors, suggesting a decreased possibility of Rac2 in the brain tumorigenesis. The role of high frequency of decreased Rac2 expression in brain tumors, particularly in malignant astrocytomas, needs further investigations to be elucidated.

Influence of MECP2 Gene Mutation and X-Chromosome Inactivation on the Rett Syndrome Phenotype

To date, approximately 200 different mutations in the MECP2 gene have been identified. We analyzed the entire coding sequence of the MECP2 gene and the X-chromosome inactivation pattern in 42 sporadic cases of Rett syndrome. Of the 42 patients, 30 had pathogenic mutations, including 14 different mutations: 9 missense mutations, 4 nonsense mutations, and 1 frameshift mutation. One was a novel mutation (S134P). There was a tendency for patients who had a nonsense mutation in the transcriptional repression domain region to show earlier onset of regression and more severe language retardation than patients with a mutation in the methyl-CpG binding domain region. However, the parameters of clinical severity were variable among patients with the same type of mutation, depending on the pattern of X-chromosome inactivation. This study suggests that the X-chromosome inactivation pattern can modify the phenotype of Rett syndrome, which is primarily determined by the type and site of MECP2 gene mutation.

Familial adenomatous polyposis: prevalence of adenomas in the ileal pouch after restorative proctocolectomy.

To determine the prevalence of adenomas in ileal pouches from patients with familial adenomatous polyposis (FAP) and to determine whether a correlation exists between the presence of pouch adenomas and duodenal adenomas and the site of the adenomatous polyposis coli gene mutation. Restorative proctocolectomy can markedly reduce the risk of colorectal adenocarcinoma in FAP patients. However, adenomas with the potential to progress to adenocarcinoma can develop in the duodenum, ileum, and continent ileostomy after restorative proctocolectomy. More recently, adenomas have been described in the ileal pouch after ileoanal anastomosis. Pouch endoscopy was offered to 167 patients with FAP who had undergone restorative proctocolectomy between January 1984 and December 1996. Adenomas were found in 35% of the 85 ileal pouches examined. No invasive carcinomas were noted. The risk of developing one or more adenomas at 5, 10, and 15 years was 7%, 35%, and 75%, respectively. Patients with adenomas were more likely to have duodenal and ampullary adenomas. No correlation was detected between adenoma development and the site of the adenomatous polyposis coli mutation. Adenomas are frequently found in the ileal pouch of patients after restorative proctocolectomy for FAP. Regular endoscopic surveillance of the pouch is recommended at a frequency similar to that of upper gastrointestinal endoscopy.

Somatic mutations of the multiple endocrine neoplasia type 1 (MEN1) gene in patients with sporadic, nonfamilial primary hyperparathyroidism

Background: Multiple endocrine neoplasia type 1 (MEN 1) is a syndrome with tumors of many endocrine tissues. Germline MEN1 gene mutations were found in most patients with familial or sporadic MEN 1. Recently, somatic MEN1 gene mutations were also detected in sporadic non-MEN 1 endocrine tumors. Methods: We used direct sequence analysis to investigate MEN1 gene mutations in 30 parathyroid tumors obtained from 30 patients with sporadic, nonfamilial primary hyperparathyroidism. Results: Four patients had somatic mutations of the MEN1 gene, comprising 1 small insertion (1091insAGC), one missense mutation (G42S), and 2 non-sense mutations (E388X, R460X). Identical missense and non-sense mutations were found in patients with familial and non-familial MEN 1. There were no differences between clinical features of patients with and without MEN1 gene mutations. Conclusions: The incidence of somatic MEN1 gene mutations (13.3%) in Japanese patients with sporadic, nonfamilial primary hyperparathyroidism is almost equal to those of such patients in the United States and Sweden. Occasionally, the MEN1 gene mutation sites in sporadic parathyroid tumors are identical to those reported in tumors from patients with familial or sporadic MEN 1. (Surgery 2000;127:337-41.)

In this Issue

In this Issue

APC gene mutations and extraintestinal phenotype of familial adenomatous polyposis.

Familial adenomatous polyposis (FAP) is caused by germline mutation of the adenomatous polyposis coli (APC) gene on chromosome 5q. This study assessed genotype-phenotype correlations for extraintestinal lesions in FAP. Mutations of the APC gene were compared with the occurrence of seven extraintestinal manifestations in 475 FAP patients from 51 families. The frequency of manifestations was adjusted for different ages of patients using person years of exposure. In pedigrees without identified APC gene mutation, analysis of linkage to chromosome 5q and/or assessment of neoplasms for replication errors characteristic of mutation in mismatch repair genes were performed. FAP patients from the 42 families (82%) with identified mutations of the APC gene had more frequent expression of extraintestinal manifestations than affected individuals without identified mutations (risk ratio 1.2-4.0; significant difference for cutaneous cysts). The presence of a cutaneous cyst or extraintestinal cancer significantly increased the likelihood of detection of a mutation in the APC gene (94% and 92% respectively; p < 0.05). In patients without identified APC gene mutation, linkage to the APC gene was found in one large family (lod = 5.1, theta 0.01), and replication error phenotype was absent in all 24 neoplasms from 16 members of these nine pedigrees. Expression of pigmented ocular fundus lesions was strongly associated with mutations in codons 541-1309, but no other extraintestinal manifestations were related to mutation position. Multiplicity of extraintestinal manifestations was high with mutation in codons 1465, 1546, and 2621. Patients with the colorectal phenotype of FAP but no extraintestinal manifestations may have non-truncating mutations of the APC gene or mutation in a gene other than APC or mismatch repair genes. The site of APC gene mutation is associated with pigmented ocular fundus lesions (codons 542-1309) and predisposition to multiplicity of extraintestinal manifestations (codons 1465, 1546, and 2621).

Congenital hypertrophy of the retinal pigment epithelium in familial adenomatous polyposis: Novel criteria of assessment and correlations with constitutional adenomatous polyposis coli gene mutations

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) is the most common extracolonic manifestation of familial adenomatous polyposis (FAP) and is an early clinical marker of the disease. It seems to be correlated with the position of constitutional mutations of the adenomatous polyposis coli (APC) gene. The authors investigated the expression of CHRPE and its correlation with the position of the APC gene in FAP patients and in "at risk" relatives from 31 FAP kindreds. To obtain comparable data on CHRPE expression, the authors developed a novel scoring system based on morphologic and dimensional criteria. A positive CHRPE score was obtained in 29 of 39 FAP patients (74%) and in 16 of 53 relatives who showed no clinical evidence of FAP (30%). Colonoscopy revealed polyps in 20 of the 47 relatives who could be examined. The cumulative sensitivity and specificity of CHRPE were 72.88% and 96.29%, respectively. APC gene mutations were characterized in 34 subjects from 17 kindreds. In 28 of the subjects, mutations were detected in exon 15, between codons 876 and 1324. Mutations were found in exon 9 in 6 subjects. In 3 of the 6 subjects, they were found at the site where both forms of alternative splicing of the exon occur (codon 437). In the other 3 subjects (another kindred), mutations were found in the portion of exon 9 in which alternative splicing occurs (codon 367). Only 1 of the 6 subjects (16.6%) with mutations in exon 9 had a positive CHRPE score, compared with 28 of 28 subjects (100%) with mutations in exon 15. None of the 3 subjects with mutations in codon 437 had a positive CHRPE score. The CHRPE scores of exon 15 mutation carriers varied markedly both within and among kindreds, irrespective of the mutation site. The results of this study indicate that the site of APC gene mutation influences CHRPE expression but is not the only factor responsible for the presence and level of retinal lesions in FAP patients.