The genetic causes of the sequential occurrence of multiple primary malignancies in a young woman--5 years on.

The finding of three primary gynaecological malignancies in a young woman attending our unit was documented in 2001. We provide an update on this report as new events have prompted further discussion on the role of clinical guidelines in cancer management. The discovery of a genetic predisposition demonstrates the need for multidisciplinary input and heightened awareness in similar cases while the importance of treating each patient as an individual is emphasized.

Comparative genomic hybridization analysis of chromosomal alterations induced by the development of resistance to thymidylate synthase inhibitors.

Acquired resistance to chemotherapy is a major obstacle to the successful treatment of cancer. In the past, technical limitations prevented the detection of genetic alterations associated with such resistance on a genome-wide scale. This study evaluated comparative genomic hybridization (CGH) as a tool to detect candidate regions of the genome associated with chemoresistance. Using a variation of conventional CGH, DNA from cell lines that were resistant to thymidylate synthase inhibitors (raltitrexed and 5-fluorouracil) and their sensitive parent cells were evaluated. In MCF-7 and H630 cells that were resistant to raltitrexed, only a single region of change (18p gain) was apparent. The third cell line, H630R10, which was resistant to 5-fluorouracil, had changes in several genomic regions following the acquisition of resistance, including 18p gain. Gain in the chromosomal region containing the thymidylate synthase gene (18p11.32) was detected by CGH in all three resistant cell lines. However, additional novel regions of interest were identified in the cells that were resistant to 5-fluorouracil. These results suggest that CGH is of potential use in the detection of regions of the genome involved in chemoresistance.

p53 mutation is a common genetic event in ovarian carcinoma.

Using the single-strand conformational polymorphism technique, we have screened 66 malignant ovarian tumors for p53 mutation in exons 5 to 8. Thirty-four of the tumors demonstrated a single-strand conformational polymorphism band shift in this region of the gene, including 6 in exon 5, 7 in exon 6, 12 in exon 7, and 10 in exon 8 (one of the tumors showed a shift for exons 7 and 8). All of the single-strand conformational polymorphism shifts have been further characterized by DNA sequencing, and 31 of 35 have been shown to represent genuine DNA alterations. These include 27 point mutations (23 missense, 2 nonsense, and 2 silent mutations), 3 deletions (a 2-base pair deletion introducing, by frameshift, a stop codon further downstream; a 3-base pair deletion; and an unusual 6-base pair deletion made up of separate 2-base pair and 4-base pair deletions), and a 4-base pair insertion (introducing a stop codon downstream). In total, 29 of the 66 (44%) carcinomas analyzed had mutations affecting the primary sequence of the p53 protein. p53 mutation was found in tumors of all International Federation of Gynecologists and Obstetricians stages, suggesting that it might be an earlier genetic event in the progression of epithelial ovarian tumors than previously thought. A significantly greater number of p53 mutations were seen in high-grade serous carcinomas than in those of endometrioid and mucinous types (0.02 > P > 0.01). Analysis of the distribution of point mutations showed no preference for any particular mutation type.

Early loss of heterozygosity on 17q in ovarian cancer. The Abe Ovarian Cancer Genetics Group.

We have studied 146 ovarian tumours (94 carcinomas, 22 tumours of low malignant potential and 30 benign tumours) for evidence of allele loss on chromosome 17p and 17q sufficient to imply the proximity of a tumour-suppressor gene. We have examined two polymorphic loci (YNZ22.2 and BHP53) on 17p13 and one on chromosome 17q (17q23-qter). Loss of heterozygosity (LOH) was detected in 34/63 (54%) informative malignant tumours at YNZ22.2 and 22/47 (47%) at BHP53; on 17q, 45/64 (70%) had LOH. Allele loss was detected in a small number of benign and borderline tumours. There was a statistically significant difference between the patterns of allele loss in serous and endometrioid groups of tumours, and allele loss occurred with significantly greater frequency on 17q than on 17p. Comparison of all malignant tumours presenting with either localized (FIGO stage I/II) or widespread (FIGO stage III/IV) disease showed that, particularly on 17q, allele loss increases in the more advanced stages. The p53 tumour-suppressor gene is implicated in ovarian carcinogenesis, and our findings suggest that an important tumour-suppressor gene may be located in the region 17q23-qter. Loss of function in this gene may be responsible for the frequently observed rapid progression of serous-type adenocarcinomas to an advanced stage.

Improving the referral process for familial breast cancer genetic counselling: findings of three randomised controlled trials of two interventions.

OBJECTIVES: To evaluate the effectiveness and cost-effectiveness of two complementary interventions, using familial breast cancer as a model condition. The primary care intervention consisted of providing computerised referral guidelines and related education to GPs. The nurse counsellor intervention evaluated genetic nurses as substitutes for specialist geneticists in the initial assessment and management of referred patients. DESIGN: The computerised referral guidelines study was a pragmatic, cluster randomised controlled trial (RCT) with general practices randomised to intervention or control groups. The nurse counsellor intervention was tested in two concurrent RCTs conducted in separate UK health service locations, using predetermined definitions of equivalence. SETTING: The computerised referral guidelines trial took place in general practices in Scotland from November 2000 to June 2001. The nurse counsellor intervention took place in a regional genetics clinic in Scotland, and in two health authorities in Wales served by a single genetics service during 2001. PARTICIPANTS: The computerised referral guidelines study involved GPs and referred patients. Both nurse counsellor intervention trials included women referred for the first time, aged 18 years or over and whose main concern was family history of breast cancer. INTERVENTIONS: The software system was developed with GPs, presenting cancer genetic referral guidelines in a checklist approach. Intervention GPs were invited to postgraduate update education sessions, and both intervention and control practices received paper-based guidelines. The intervention period was November 2000 to June 2001. For the nurse counsellor trial, trial 1 ran outpatient sessions with the same appointment length as the standard service offered by geneticists, but the nurse counsellor saw new patients at the first appointment and referred back to the GP or on to a clinical geneticist according to locally developed protocol, under the supervision of a consultant geneticist. The control intervention was the current service, which comprised an initial and a follow-up appointment with a clinical geneticist. In trial 2, a nurse counsellor ran outpatient sessions with the same appointment length as the new consultant-based cancer genetics service and new patients were seen at the first appointment and referred as in trial 1. The control intervention was a new service, and comprised collection of family history by telephone followed by a consultation with a clinical assistant or a specialist registrar, supervised by a consultant. The intervention was implemented between 1998 and 2001. MAIN OUTCOME MEASURES: In the software system trial, the primary outcome was GPs' confidence in their management of patients with concerns about family history of breast cancer. For the nurse counsellor trial, the primary outcome was patient anxiety, measured using standard scales. RESULTS: In the software system trial, 57 practices (230 GPs) were randomised to the intervention group and 29 (116 GPs) to the control group. No statistically significant differences were detected in GPs' confidence or any other outcomes. Fewer than half of the intervention GPs were aware of the software, and only 22 reported using it in practice. The estimated total cost was GBP3.12 per CD-ROM distributed (2001 prices). For the two arms of the nurse counsellor trial, 289 patients (193 intervention, 96 control) and 297 patients (197 intervention and 100 control) consented, were randomised, returned a baseline questionnaire and attended the clinic for trials 1 and 2 respectively. The analysis in both cases suggested equivalence in all anxiety scores, and no statistically significant differences were detected in other outcomes in either trial. A cost-minimisation analysis suggested that the cost per counselling episode was GBP10.23 lower in intervention arm than in the control arm and GBP10.89 higher in the intervention arm than in the control arm (2001 prices) for trials 1 and 2, respectively. Taking the trials together, the costs were sensitive to the grades of doctors and the time spent in consultant supervision of the nurse counsellor, but they were only slightly affected by the grade of nurse counsellor, the selected discount rate and the lifespan of equipment. CONCLUSIONS: Computer-based systems in the primary care intervention cannot be recommended for widespread use without further evaluation and testing in real practice settings. Genetic nurse counsellors may be a cost-effective alternative to assessment by doctors. This trial does not provide definitive evidence that the general policy of employing genetics nurse counsellors is sound, as it was based on only three individuals. Future evaluations of computer-based decision support systems for primary care must first address their efficacy under ideal conditions, identify barriers to the use of such systems in practice, and provide evidence of the impact of the policy of such systems in routine practice. The nurse counsellor trial should be replicated in other settings to provide reassurance of the generalisability of the intervention and other models of nurse-based assessment, such as in outreach clinics, should be developed and evaluated. The design of future evaluations of professional substitution should also address issues such as the effect of different levels of training and experience of nurse counsellors, and learning effects.

Aortic blood velocity measurement in healthy adults using a simple ultrasound technique.

The normal range of aortic blood velocity has been established in 140 healthy adults using the non-invasive technique of transcutaneous aortovelography (TAV). Velocity is independent of sex, body surface area and blood pressure but declines progressively with age so that at age 70 the mean value of peak velocity is 55% of that at age 20. Integration of the area under the velocity time curve gives an indication of stroke volume and cardiac output. These indices also decrease with age as does acceleration which may reflect left ventricular function. Measurement of aortic blood velocity and its derivatives is a safe, simple and physiologically meaningful way of assessing cardiac output and function.

Paget's disease of bone: evidence for a susceptibility locus on chromosome 18q and for genetic heterogeneity.

Paget's disease of bone is a common condition characterized by bone pain, deformity, pathological fracture, and an increased incidence of osteosarcoma. Genetic factors play a role in the pathogenesis of Paget's disease but the molecular basis of the disease remains unclear. Previous genetic linkage studies have mapped the rare Paget's disease-like bone dysplasia familial expansile osteolysis (FEO) to chromosome 18q21-22, and recent work has shown evidence of linkage between this locus and Paget's disease in one family. Here we studied the relationship between the 18q21-22 locus and Paget's disease in eight large multiplex families from diverse ethnic backgrounds with inherited Paget's disease. Paget's disease was inherited as an autosomal dominant trait in all families, with high penetrance by the sixth decade. Analysis of seven highly polymorphic markers from chromosome 18q21-22 showed positive summated two-point log10 odds ratio (lodscores) of +2.97 with the marker D18S42 at a recombination fraction (theta) = 0.05, and of +2.95 with the marker D18S60 at theta = 0.00, values which are close to the cut-off of +3.0, which is generally accepted as evidence of linkage. Segregation analysis of the haplotypes and formal statistical analysis using the HOMOG program provided evidence for genetic heterogeneity, however, with evidence for linkage in five families and against linkage in the remaining three families (chi square 8.82; df = 2; p < 0.025). Multipoint linkage analysis in the five linked families showed lodscores of above +3.5 across the whole susceptibility region and a maximum summated lodscore of 3.89 at the marker D18S465. In the three nonlinked families, negative multipoint results were obtained for the whole region, with lodscores below -2.0 in one family, excluding this as a candidate locus for the disease. Our studies demonstrate the importance of hereditary factors in the pathogenesis of Paget's disease and confirm evidence of linkage between Paget's disease and chromosome 18q21-22 in some families. This raises the possibility that Paget's disease and FEO may share a common molecular basis, perhaps due to different mutations in the same gene or family of genes. Data from three families did not support evidence of linkage to 18q21-22 however, indicating that Paget's disease is genetically heterogeneous and suggests the presence of at least one additional locus which remains to be discovered.

Rapid diagnosis and identification of cross-over sites in patients with glucocorticoid remediable aldosteronism.

Glucocorticoid remediable aldosteronism (GRA) is an autosomal dominant cause of primary aldosteronism and high blood pressure resulting from a chimeric 11beta-hydroxylase/aldosterone synthase gene. Abnormal expression of aldosterone synthase causes primary aldosteronism, which can be inhibited by glucocorticoids. Diagnosis of GRA has depended on the identification of a restriction enzyme product in genomic DNA of affected individuals. Recently, a two-tube long PCR method was described that allowed diagnosis of GRA in a kindred in Australia. A similar long PCR method confirmed the diagnosis of GRA in members of five northeastern Scotland families previously identified by Southern blotting and detected affected members of five GRA families previously identified in Glasgow. A multiplex PCR protocol is described here that allows the control aldosterone synthase amplification and chimeric gene amplification to be carried out in the same tube. We describe the regions of cross-over in each of 10 kindreds identified in Scotland. To identify cross-over regions in each of the kindreds, the chimeric long PCR product was cloned and sequenced. Five cross-over sites were identified ranging from intron 2 to exon 4, indicating the reliability of the method in identifying chimeric genes resulting from different sites of cross-over.

Epidermal growth factor (EGF) increases the in vitro invasion, motility and adhesion interactions of the primary renal carcinoma cell line, A704.

Metastasis is a multistep process that involves alterations in a tumour cell's invasion, motility and adhesive capabilities. This study examined the effect of EGF on the in vitro invasion, motility and adhesion of the primary renal adenocarcinoma cell line, A704. Stimulation of the tumour cells by EGF (40 ng/ml) for a period of 24 h increased the in vitro invasion (P = 0.040) and motility (P = 0.039). Cell adhesion was examined on fibronectin, laminin, collagen IV and a 1:1:1 mix of the three extracellular matrix components. After EGF (40 ng/ml) stimulation, adhesion was significantly decreased on fibronectin (P = 0.022) and collagen type IV (P = 0.026), but increased on the 1:1:1 mix of extracellular matrix components (P = 0.022). The 92 kDa matrix metalloproteinase (MMP-9) present in the cell-conditioned medium was also increased after a 24 h stimulation with EGF (40 ng/ml) when measured. Hence, EGF can modulate the in vitro invasion, motility, adhesiveness and matrix metalloproteinase production in the A704 cell line, and subsequently may have a role in the metastatic potential of some renal carcinomas.

Polymorphisms in P21CIP1/WAF1 are not correlated with TP53 status in sporadic ovarian tumours.

In breast cancers and sarcomas, a variant polymorphism in the cell cycle inhibitor P21CIP1/WAF1 is under-represented in those individuals whose tumours contain mutated TP53. The aim of this study was to determine whether this variant polymorphism was also under-represented in those with ovarian carcinoma and TP53 mutations. We studied lymphocyte DNA from 104 women with ovarian carcinoma, 15 with borderline tumours and 16 with benign tumours, using a previously-reported PCR-RFLP technique. 96 of the ovarian carcinoma cases had been previously examined for mutations in TP53 and/or for overexpression of the TP53 protein. The variant allele was seen in 11 out of 104 women (10.6%) with ovarian carcinoma. There was no significant difference in the distribution of the variant allele in the women whose tumours had (7/47) or did not have (4/49) TP53 mutations (P = 0.523). It does not appear that the presence of this variant allele of P21CIP1/WAF1 has any aetiological role in ovarian carcinomas. Studies in other tumours support this finding.

Current policies for surveillance and management in women at risk of breast and ovarian cancer: a survey among 16 European family cancer clinics. European Familial Breast Cancer Collaborative Group.

The recent isolation of breast cancer predisposing genes (BRCA1 and BRCA2) allows the identification of carriers within affected families. These carriers have a 50-85% risk of developing breast or ovarian cancer and need careful follow-up. The purpose of this study was to evaluate the management and screening protocols implemented in high risk families at various family cancer clinics in Europe. A questionnaire was mailed to the members of the European Familial Breast Cancer Collaborative Group (n = 30) requesting information on the following issues: indication for surveillance of breasts and ovaries, the recommended protocol, coordination of the screening examination, prophylactic surgery, the specific management of breast cancer in a mutation carrier and the use of oestrogen. 16 centres from nine countries responded. Most centres recommend surveillance of the breasts if the lifetime risk exceeds 15-20%. The surveillance protocol that is generally advised comprises monthly self breast examination, examination by a specialist every 6 months and annual mammography, all starting from an age between 25 and 35 years. Surveillance of the ovaries is recommended in BRCA1 and BRCA2-mutation carriers, in members from breast/ovarian cancer families and in some centres in 'breast cancer only' families with an early onset of breast cancer. The recommended protocol includes gynaecological examination, sonography and estimation of CA-125 at yearly intervals starting from the age 30-35 years. Prophylactic mastectomy is considered for proven mutation carriers in some centres. Most centres consider prophylactic oophorectomy in mutation carriers and some centres also consider it for members of breast/ovarian cancer families. This survey provides insight into the guidelines for surveillance and management of familial breast cancer used at various family cancer clinics in Europe; this insight may contribute to the appropriate management of these high risk women. It should be emphasised that most recommendations are based on experts' opinion rather than on any specific studies.

Prothrombotic genotypes are not associated with pre-eclampsia and gestational hypertension: results from a large population-based study and systematic review.

DNA samples collected as part of a large population-based case-control study were genotyped to examine the associations of five prothrombotic gene polymorphisms with pre-eclampsia (PE) and gestational hypertension (GH). The polymorphisms studied were: G1691A in Factor V (Factor V Leiden; FVL), prothrombin G20210A, methylenetetrahydrofolate reductase (MTHFR) C677T, plasminogen activator inhibitor-1 4G/5G and the platelet collagen receptor alpha2beta1 C807T. A group of 404 women who developed PE were retrospectively compared with 303 women with GH and 164 control women. The frequency of genotypes did not differ significantly between cases of PE or GH and controls for any of the five polymorphisms studied. We conclude that these prothrombotic genotypes are not associated with the development of PE or GH in our population. The systematic review supports our conclusion, for all but cases of severe disease. which appear to be associated with FVL and, to a lesser extent, MTHFR C677T. There is little value in antenatal screening for prothrombotic polymorphisms to predict the development of pre-eclampsia or gestational hypertension.

Folate and breast cancer: the role of polymorphisms in methylenetetrahydrofolate reductase (MTHFR).

Evidence is growing that low folate status may be a factor in the aetiology of several cancers, including breast cancer. The methylenetetrahydrofolate reductase gene (MTHFR), which has a key role in folate metabolism, is polymorphic. We report a case-control study of two functional polymorphisms in MTHFR, dietary folate intake and breast cancer. Sixty-two cases with invasive breast cancer and sixty-six general practice controls participated. Women reporting the highest dietary folate intake had non-significantly reduced breast cancer risk (odds ratio (OR) = 0.49, 95% confidence interval (CI) 0.20-1.20). Risk was significantly lower for the 1298CC genotype compared to AA (OR = 0.24, 95% CI 0.06-0.97). Relative to compound wild-type subjects, compound heterozygotes had moderately reduced risk (OR = 0.47, 95% CI 0.11-1.92) and homozygote variants (677TT and/or 1298CC) greater reduced risk (OR = 0.26, 95% CI 0.07-0.96); the trend was statistically significant. Patterns in risk with regard to genotype and folate combinations are broadly similar those reported for colorectal neoplasia. The roles of MTHFR and folate in breast cancer aetiology are likely to be complex.

Germ line BRCA1 & BRCA2 mutations in Greek breast/ovarian cancer families: 5382insC is the most frequent mutation observed.

BRCA1 and BRCA2 genes were screened for loss-of-function mutations in a series of 85 patients having at least one first- or second-degree relative affected by breast and/or ovarian cancer. All BRCA1 exons and BRCA2 exons 10 and 11 were screened with a combination of methods including SSCP, PTT and direct sequencing. We have found disease-associated mutations in 14 families (16.5%), eleven in BRCA1 and three in BRCA2. The known founder mutation 5382insC of BRCA1 was identified in seven unrelated families. The other mutations identified include the non-sense R1751X, the splice junction variant 5586G>A of BRCA1 and three frameshifts, 2024del5, 3034del4, and 6631del5, of BRCA2. Nine out of these 14 families had a family history of three or more breast/ovarian cancer cases. A large number of polymorphic or unclassified variants is also reported. Combined with our previously published data 5382insC was found in nine out of 20 families (45%), suggesting that this mutation may represent a common founder mutation in the Greek population.

A protective role for common p21WAF1/Cip1 polymorphisms in human ovarian cancer.

The objective of this study was to compare the frequency of two common p21WAF1/Cip1 gene polymorphisms in ovarian cancer patients with that in age-matched controls, from a population originating from Eastern Scotland. Both polymorphisms were found significantly less frequently in both the constitutive and tumour tissue DNA of ovarian cancer patients (3/65; 4.6%), than in that from geographically and age-matched controls (25/186; 13.4%) (p=0.0495, chi2). Furthermore, we found no p21WAF1/Cip1 gene mutations in any of the tumours, reflected by a relatively low degree of loss of heterozygosity (LOH) at the chromosomal region where the gene maps, providing further evidence that the p21WAF1/Cip1 gene is not mutated in ovarian cancer. The data suggest however, that there may potentially be a protective function for the two p21WAF1/Cip1 gene polymorphisms in the population under study.

Significant telomere shortening in childhood leukemia.

Telomere length was studied by Southern analysis in five cases of childhood acute leukemia. In four cases, the length of the telomere sequence of the blast phase cells was shortened as compared with that of the cells examined during remission. Study of telomere length during chemotherapy for hematologic malignancies may show rapidly dividing subpopulations of malignant cells and thereby guide further treatment needs. In addition, such loss of telomere sequence would give rise to chromosomal instability and could be one of the mechanisms of oncogene activation in acute leukemia.

Is random screening of value in detecting glucocorticoid-remediable aldosteronism within a hypertensive population?

INTRODUCTION: Glucocorticoid-remediable aldosteronism (GRA) is a rare inherited cause for hypertension associated with a significant morbidity and mortality at an early age. Individuals with this abnormality frequently present with severe hypertension which is resistant to standard antihypertensive therapy, a strong family history of hypertension, intracranial haemorrhage, and sporadic hypokalaemia. However many affected individuals may appear phenotypically indistinguishable from normal essential hypertensives but remain at high risk of morbidity and mortality. OBJECTIVE: To determine how effective random or targeted screening of hypertensive patients is for the detection of GRA. DESIGN: A prospective study involving the screening of 300 hypertensive patients chosen at random attending the Aberdeen Hypertension Clinic and, during the same period, the targeted screening of patients with a medical and family history suggestive of GRA. SETTING: A University hospital with a primary catchment of 500,000 inhabitants and a hypertension clinic population of over 8500 patients. RESULTS: Random screening failed to identify any GRA mutation-positive individuals. Targeted screening of selected individuals revealed two index families and four further families containing 40 mutation-positive individuals. CONCLUSION: Targeted screening of hypertensive individuals with a family history of hypertension, cerebral haemorrhage, a history of hypertension from an early age, resistant hypertension which has proven difficult to control and hypokalaemia revealed two index cases and four further individuals and 30 hypertensive and 10 normotensive members of their families with GRA.

Immunohistochemical detection of a germline BRCA1 mutation in a breast and ovarian cancer family.

Tumours from four individuals in a breast and ovarian cancer family with a known deleterious germline BRCA1 mutation, were analyzed using BRCA1 antibodies. In addition, we examined tumours from 96 female patients with early-onset breast cancer, who were not selected because of any family history. Paraffin-embedded tumour sections were examined by standard immunohistochemical analysis. Three familial tumours from BRCA1 carriers displayed focal negativity. This observation was not seen in a non-mutation carrier from the same family. It was found that 9/96 (9%) early-onset breast tumours had total BRCA1 negativity. In addition, 2/2 (100%) medullary breast carcinomas displayed negativity for both antibodies. Our results indicate that BRCA1 antibodies can discriminate between familial tumours with and without a deleterious mutation from one family. Further mutation studies in early-onset breast cancer group will be necessary to evaluate the use of immunohistochemistry as a rapid, initial screening technique to identify BRCA1 mutations.

Inactivation of the p16INK4A gene by methylation is not a frequent event in sporadic ovarian carcinoma.

The p16INK4A tumour suppressor gene (p16) encodes for a cyclin-dependant kinase inhibitor which plays a role in the phosphorylation of the retinoblastoma protein (pRb) during regulation of the G1-S phase of the cell cycle. Loss of heterozygosity at 9p21, the chromosomal location of the p16 gene, has been reported in a broad range of tumours and this is usually indicative of the presence of a tumour suppressor gene, the second allele being frequently inactivated by mutation or deletion. The p16 gene, however, is often found not be mutated or deleted and it has been suggested that hypermethylation of the CpG islands of the gene may be an alternative mechanism of gene inactivation. We sought to determine the levels of p16 abnormality in a series of epithelial ovarian carcinomas in an attempt to clarify the presently conflicting evidence of whether or not hypermethylation of the p16 gene plays a role in ovarian carcinogenesis. We analysed 57 primary ovarian tumours and their corresponding blood DNA using SSCP analysis, sequencing and the methylation specific PCR (MSP) technique. We found low levels of mutation (6.7% of malignant tumours) and no evidence of methylation in any of our samples, suggesting that neither mutation or hypermethylation of the CpG islands of the p16 gene play an important role in ovarian carcinogenesis.

Rhodopsin mutations in a Scottish retinitis pigmentosa population, including a novel splice site mutation in intron four.

Retinitis pigmentosa (RP) is the name given to a group of disorders, both clinically and genetically heterogeneous, that primarily affect the photoreceptor function of the eye. Mutations in the genes encoding for rhodopsin, RDS-peripherin, or the beta subunit of the cGMP phosphodiesterase enzyme can be responsible for the phenotype. In this study the rhodopsin gene has been screened for mutations in a panel of RP individuals and five different sequence changes have been detected to date in three dominantly inherited and two unclassified families. One of these, a base substitution in the 3'UTR, has not yet been confirmed as disease specific, while three missense substitutions have previously been reported and are likely to be responsible for the phenotype. The fifth change, a base substitution at the intron 4 acceptor splice site, represents a novel mutation and is assumed to be the causative mutation.