The heterogeneous cancer phenotype of individuals with biallelic germline pathogenic variants in CHEK2

PURPOSE

Females with biallelic CHEK2 germline pathogenic variants (gPVs) more often develop multiple breast cancers than individuals with monoallelic CHEK2 gPVs. This study is aimed at expanding the knowledge on the occurrence of other malignancies.

METHODS

Exome sequencing of individuals who developed multiple primary malignancies identified 3 individuals with the CHEK2 (NM_007194.4) c.1100del p.(Thr367MetfsTer15) loss-of-function gPV in a biallelic state. We collected the phenotypes of an additional cohort of individuals with CHEK2 biallelic gPVs (n = 291).

RESULTS

In total, 157 individuals (53.4%; 157/294 individuals) developed ≥1 (pre)malignancy. The most common (pre)malignancies next to breast cancer were colorectal- (n = 19), thyroid- (n = 19), and prostate (pre)malignancies (n = 12). Females with biallelic CHEK2 loss-of-function gPVs more frequently developed ≥2 (pre)malignancies and at an earlier age compared with females biallelic for the CHEK2 c.470T>C p.(Ile157Thr) missense variant. Furthermore, 26 males (31%; 26/84 males) with CHEK2 biallelic gPVs developed ≥1 (pre)malignancies of 15 origins.

CONCLUSION

Our study suggests that CHEK2 biallelic gPVs likely increase the susceptibility to develop multiple malignancies in various tissues, both in females and males. However, it is possible that a substantial proportion of individuals with CHEK2 biallelic gPVs is missed as diagnostic testing for CHEK2 often is limited to individuals who developed breast cancer.

TINF2 is a haploinsufficient tumor suppressor that limits telomere length

Telomere shortening is a presumed tumor suppressor pathway that imposes a proliferative barrier (the Hayflick limit) during tumorigenesis. This model predicts that excessively long somatic telomeres predispose to cancer. Here, we describe cancer-prone families with two unique TINF2 mutations that truncate TIN2, a shelterin subunit that controls telomere length. Patient lymphocyte telomeres were unusually long. We show that the truncated TIN2 proteins do not localize to telomeres, suggesting that the mutations create loss-of-function alleles. Heterozygous knock-in of the mutations or deletion of one copy of TINF2 resulted in excessive telomere elongation in clonal lines, indicating that TINF2 is haploinsufficient for telomere length control. In contrast, telomere protection and genome stability were maintained in all heterozygous clones. The data establish that the TINF2 truncations predispose to a tumor syndrome. We conclude that TINF2 acts as a haploinsufficient tumor suppressor that limits telomere length to ensure a timely Hayflick limit.

Evaluation of yield and experiences of age-related molecular investigation for heritable and nonheritable causes of mismatch repair deficient colorectal cancer to identify Lynch syndrome

Universal mismatch repair deficiency (dMMR) testing of colorectal cancer (CRC) is promoted as routine diagnostics to prescreen for Lynch syndrome. We evaluated the yield and experience of age-related molecular investigation for heritable and nonheritable causes of dMMR in CRC below age 70 to identify Lynch Syndrome. In a prospective cohort of 3602 newly diagnosed CRCs below age 70 from 19 hospitals, dMMR, MLH1 promoter hypermethylation, germline MMR gene and somatic MMR gene testing was assessed in daily practice. Yield was evaluated using data from the Dutch Pathology Registry (PALGA) and two regional genetic centers. Experiences of clinicians were evaluated through questionnaires. Participating clinicians were overwhelmingly positive about the clinical workflow. Pathologists routinely applied dMMR-testing in 84% CRCs and determined 10% was dMMR, largely due to somatic MLH1 hypermethylation (66%). Of those, 69% with dMMR CRC below age 70 without hypermethylation were referred for genetic testing, of which 55% was due to Lynch syndrome (hereditary) and 43% to somatic biallelic pathogenic MMR (nonhereditary). The prevalence of Lynch syndrome was 18% in CRC < 40, 1.7% in CRC age 40-64 and 0.7% in CRC age 65-69. Age 65-69 represents most cases with dMMR, in which dMMR due to somatic causes (13%) is 20 times more prevalent than Lynch syndrome. In conclusion, up to age 65 routine diagnostics of (non-)heritable causes of dMMR CRCs effectively identifies Lynch syndrome and reduces Lynch-like diagnoses. Above age 64, the effort to detect one Lynch syndrome patient in dMMR CRC is high and germline testing rarely needed.

The Apparent Genetic Anticipation in PMS2-Associated Lynch Syndrome Families Is Explained by Birth-cohort Effect

BACKGROUND

PMS2-associated Lynch syndrome is characterized by a relatively low colorectal cancer penetrance compared with other Lynch syndromes. However, age at colorectal cancer diagnosis varies widely, and a strong genetic anticipation effect has been suggested for PMS2 families. In this study, we examined proposed genetic anticipation in a sample of 152 European PMS2 families.

METHODS

The 152 families (637 family members) that were eligible for analysis were mainly clinically ascertained via clinical genetics centers. We used weighted Cox-type random effects model, adjusted by birth cohort and sex, to estimate the generational effect on the age of onset of colorectal cancer. Probands and young birth cohorts were excluded from the analyses. Weights represented mutation probabilities based on kinship coefficients, thus avoiding testing bias.

RESULTS

Family data across three generations, including 123 colorectal cancers, were analyzed. When compared with the first generation, the crude HR for anticipation was 2.242 [95% confidence interval (CI), 1.162-4.328] for the second generation and 2.644 (95% CI, 1.082-6.464) for the third generation. However, after correction for birth cohort and sex, the effect vanished [HR = 1.302 (95% CI, 0.648-2.619) and HR = 1.074 (95% CI, 0.406-2.842) for second and third generations, respectively].

CONCLUSIONS

Our study did not confirm previous reports of genetic anticipation in PMS2-associated Lynch syndrome. Birth-cohort effect seems the most likely explanation for observed younger colorectal cancer diagnosis in subsequent generations, particularly because there is currently no commonly accepted biological mechanism that could explain genetic anticipation in Lynch syndrome.

IMPACT

This new model for studying genetic anticipation provides a standard for rigorous analysis of families with dominantly inherited cancer predisposition.

Cancer Risks for PMS2-Associated Lynch Syndrome

PURPOSE

Lynch syndrome due to pathogenic variants in the DNA mismatch repair genes MLH1, MSH2, and MSH6 is predominantly associated with colorectal and endometrial cancer, although extracolonic cancers have been described within the Lynch tumor spectrum. However, the age-specific cumulative risk (penetrance) of these cancers is still poorly defined for PMS2-associated Lynch syndrome. Using a large data set from a worldwide collaboration, our aim was to determine accurate penetrance measures of cancers for carriers of heterozygous pathogenic PMS2 variants.

METHODS

A modified segregation analysis was conducted that incorporated both genotyped and nongenotyped relatives, with conditioning for ascertainment to estimates corrected for bias. Hazard ratios (HRs) and corresponding 95% CIs were estimated for each cancer site for mutation carriers compared with the general population, followed by estimation of penetrance.

RESULTS

In total, 284 families consisting of 4,878 first- and second-degree family members were included in the analysis. PMS2 mutation carriers were at increased risk for colorectal cancer (cumulative risk to age 80 years of 13% [95% CI, 7.9% to 22%] for males and 12% [95% CI, 6.7% to 21%] for females) and endometrial cancer (13% [95% CI, 7.0%-24%]), compared with the general population (6.6%, 4.7%, and 2.4%, respectively). There was no clear evidence of an increased risk of ovarian, gastric, hepatobiliary, bladder, renal, brain, breast, prostate, or small bowel cancer.

CONCLUSION

Heterozygous PMS2 mutation carriers were at small increased risk for colorectal and endometrial cancer but not for any other Lynch syndrome-associated cancer. This finding justifies that PMS2-specific screening protocols could be restricted to colonoscopies. The role of risk-reducing hysterectomy and bilateral salpingo-oophorectomy for PMS2 mutation carriers needs further discussion.

Molecular Background of Colorectal Tumors From Patients With Lynch Syndrome Associated With Germline Variants in PMS2

BACKGROUND & AIMS

Germline variants in mismatch repair genes MLH1, MSH2 (EPCAM), MSH6, or PMS2 cause Lynch syndrome. Patients with these variants have an increased risk of developing colorectal cancers (CRCs) that differ from sporadic CRCs in genetic and histologic features. It has been a challenge to study CRCs associated with PMS2 variants (PMS2-associated CRCs) because these develop less frequently and in older patients than CRCs with variants in other mismatch repair genes.

METHODS

We analyzed 20 CRCs associated with germline variants in PMS2, 22 sporadic CRCs, 18 CRCs with germline variants in MSH2, and 24 CRCs from patients with germline variants in MLH1. Tumor tissue blocks were collected from Dutch pathology departments in 2017. After extraction of tumor DNA, we used a platform designed to detect approximately 3,000 somatic hotspot variants in 55 genes (including KRAS, APC, CTNNB1, and TP53). Somatic variant frequencies were compared using the Fisher exact test.

RESULTS

None of the PMS2-associated CRCs contained any somatic variants in the catenin-β₁ gene (CTNNB1), which encodes β-catenin, whereas 14 of 24 MLH1-associated CRCs (58%) contained variants in CTNNB1. Half the PMS2-associated CRCs contained KRAS variants, but only 20% of these were in hotspots that encoded G12D or G13D. These hotspot variants occurred more frequently in CRCs associated with variants in MLH1 (37.5%; P = .44) and MSH2 (71.4%; P = .035) than in those associated with variants in PMS2.

CONCLUSIONS

In a genetic analysis of 84 colorectal tumors, we found tumors from patients with PMS2-associated Lynch syndrome to be distinct from colorectal tumors associated with defects in other mismatch repair genes. This might account for differences in development and less frequent occurrence.

Clinical Aspects of SDHA-Related Pheochromocytoma and Paraganglioma: A Nationwide Study

CONTEXT

Paraganglioma (PGL) has the highest degree of heritability among human neoplasms. Current clinical understanding of germline SDHA mutation carriers is limited.

OBJECTIVE

To estimate the contribution of SDHA mutations in PGL and to assess clinical manifestations and age-related penetrance.

DESIGN

Nationwide retrospective cohort study.

SETTING

Tertiary referral centers in the Netherlands (multicenter).

PATIENTS

Germline SDHA analysis was performed in 393 patients with genetically unexplained PGL. Subsequently, 30 index SDHA mutation carriers and 56 nonindex carriers were studied.

MAIN OUTCOME MEASURES

SDHA mutation detection yield, clinical manifestations, and SDHA-related disease penetrance.

RESULTS

Pathogenic germline SDHA variants were identified in 30 of the 393 referred patients with PGL (7.6%), who had head and neck PGL (21 of 174 [12%]), pheochromocytoma (4 of 191 [2%]), or sympathetic PGL (5 of 28 [18%]). The median age at diagnosis was 43 years (range, 17 to 81 years) in index SDHA mutation carriers compared with 52 years (range, 7 to 90 years) in nonmutation carriers (P = 0.002). The estimated penetrance of any SDHA-related manifestation was 10% at age 70 years (95% confidence interval, 0% to 21%) in nonindex mutation carriers.

CONCLUSION

Germline SDHA mutations are relatively common (7.6%) in patients with genetically unexplained PGL. Most index patients presented with apparently sporadic PGL. In this SDHA series, the largest assembled so far, we found the lowest penetrance of all major PGL predisposition genes. This suggests that recommendations for genetic counseling of at-risk relatives and stringency of surveillance for SDHA mutation carriers might need to be reassessed.

Role of germline aberrations affecting CTNNA1, MAP3K6 and MYD88 in gastric cancer susceptibility

BACKGROUND

In approximately 10% of all gastric cancer (GC) cases, a heritable cause is suspected. A subset of these cases have a causative germline CDH1 mutation; however, in most cases the cause remains unknown. Our objective was to assess to what extent these remaining cases may be explained by germline mutations in the novel candidate GC predisposing genes CTNNA1, MAP3K6 or MYD88.

METHODS

We sequenced a large cohort of unexplained young and/or familial patients with GC (n=286) without a CDH1germline mutation for germline variants affecting CTNNA1, MAP3K6 and MYD88 using a targeted next-generation sequencing approach based on single-molecule molecular inversion probes.

RESULTS

Predicted deleterious germline variants were not encountered in MYD88, but recurrently observed in CTNNA1 (n=2) and MAP3K6 (n=3) in our cohort of patients with GC. In contrast to deleterious variants in CTNNA1, deleterious variants in MAP3K6 also occur frequently in the general population.

CONCLUSIONS

Based on our results MAP3K6 should no longer be considered a GC predisposition gene, whereas deleterious CTNNA1 variants are confirmed as an infrequent cause of GC susceptibility. Biallelic MYD88 germline mutations are at most a very rare cause of GC susceptibility as no additional cases were identified.

Unraveling genetic predisposition to familial or early onset gastric cancer using germline whole-exome sequencing

Recognition of individuals with a genetic predisposition to gastric cancer (GC) enables preventive measures. However, the underlying cause of genetic susceptibility to gastric cancer remains largely unexplained. We performed germline whole-exome sequencing on leukocyte DNA of 54 patients from 53 families with genetically unexplained diffuse-type and intestinal-type GC to identify novel GC-predisposing candidate genes. As young age at diagnosis and familial clustering are hallmarks of genetic tumor susceptibility, we selected patients that were diagnosed below the age of 35, patients from families with two cases of GC at or below age 60 and patients from families with three GC cases at or below age 70. All included individuals were tested negative for germline CDH1 mutations before or during the study. Variants that were possibly deleterious according to in silico predictions were filtered using several independent approaches that were based on gene function and gene mutation burden in controls. Despite a rigorous search, no obvious candidate GC predisposition genes were identified. This negative result stresses the importance of future research studies in large, homogeneous cohorts.

Identification of new TRIP12 variants and detailed clinical evaluation of individuals with non-syndromic intellectual disability with or without autism

The ubiquitin pathway is an enzymatic cascade including activating E1, conjugating E2, and ligating E3 enzymes, which governs protein degradation and sorting. It is crucial for many physiological processes. Compromised function of members of the ubiquitin pathway leads to a wide range of human diseases, such as cancer, neurodegenerative diseases, and neurodevelopmental disorders. Mutations in the thyroid hormone receptor interactor 12 (TRIP12) gene (OMIM 604506), which encodes an E3 ligase in the ubiquitin pathway, have been associated with autism spectrum disorder (ASD). In addition to autistic features, TRIP12 mutation carriers showed intellectual disability (ID). More recently, TRIP12 was postulated as a novel candidate gene for intellectual disability in a meta-analysis of published ID cohorts. However, detailed clinical information characterizing the phenotype of these individuals was not provided. In this study, we present seven novel individuals with private TRIP12 mutations including two splice site mutations, one nonsense mutation, three missense mutations, and one translocation case with a breakpoint in intron 1 of the TRIP12 gene and clinically review four previously published cases. The TRIP12 mutation-positive individuals presented with mild to moderate ID (10/11) or learning disability [intelligence quotient (IQ) 76 in one individual], ASD (8/11) and some of them with unspecific craniofacial dysmorphism and other anomalies. In this study, we provide detailed clinical information of 11 TRIP12 mutation-positive individuals and thereby expand the clinical spectrum of the TRIP12 gene in non-syndromic intellectual disability with or without ASD.

Allelic Mutations of KITLG, Encoding KIT Ligand, Cause Asymmetric and Unilateral Hearing Loss and Waardenburg Syndrome Type 2

Linkage analysis combined with whole-exome sequencing in a large family with congenital and stable non-syndromic unilateral and asymmetric hearing loss (NS-UHL/AHL) revealed a heterozygous truncating mutation, c.286_303delinsT (p.Ser96Ter), in KITLG. This mutation co-segregated with NS-UHL/AHL as a dominant trait with reduced penetrance. By screening a panel of probands with NS-UHL/AHL, we found an additional mutation, c.200_202del (p.His67_Cys68delinsArg). In vitro studies revealed that the p.His67_Cys68delinsArg transmembrane isoform of KITLG is not detectable at the cell membrane, supporting pathogenicity. KITLG encodes a ligand for the KIT receptor. Also, KITLG-KIT signaling and MITF are suggested to mutually interact in melanocyte development. Because mutations in MITF are causative of Waardenburg syndrome type 2 (WS2), we screened KITLG in suspected WS2-affected probands. A heterozygous missense mutation, c.310C>G (p.Leu104Val), that segregated with WS2 was identified in a small family. In vitro studies revealed that the p.Leu104Val transmembrane isoform of KITLG is located at the cell membrane, as is wild-type KITLG. However, in culture media of transfected cells, the p.Leu104Val soluble isoform of KITLG was reduced, and no soluble p.His67_Cys68delinsArg and p.Ser96Ter KITLG could be detected. These data suggest that mutations in KITLG associated with NS-UHL/AHL have a loss-of-function effect. We speculate that the mechanism of the mutation underlying WS2 and leading to membrane incorporation and reduced secretion of KITLG occurs via a dominant-negative or gain-of-function effect. Our study unveils different phenotypes associated with KITLG, previously associated with pigmentation abnormalities, and will thereby improve the genetic counseling given to individuals with KITLG variants.

High Satisfaction and Low Distress in Breast Cancer Patients One Year after BRCA-Mutation Testing without Prior Face-to-Face Genetic Counseling

According to standard practice following referral to clinical genetics, most high risk breast cancer (BC) patients in many countries receive face-to-face genetic counseling prior to BRCA-mutation testing (DNA-intake). We evaluated a novel format by prospective study: replacing the intake consultation with telephone, written and digital information sent home. Face-to-face counseling then followed BRCA-mutation testing (DNA-direct). One year after BRCA-result disclosure, 108 participants returned long-term follow-up questionnaires, of whom 59 (55 %) had previously chosen DNA-direct (intervention) versus DNA-intake (standard practice i.e., control: 45 %). Questionnaires assessed satisfaction and psychological distress. All participants were satisfied and 85 % of DNA-direct participants would choose this procedure again; 10 % would prefer DNA-intake and 5 % were undecided. In repeated measurements ANOVA, general distress (GHQ-12, p = 0.01) and BC-specific distress (IES-bc, p = 0.03) were lower in DNA-direct than DNA-intake at all time measurements. Heredity-specific distress (IES-her) did not differ significantly between groups. Multivariate regression analyses showed that choice of procedure did not significantly contribute to either general or heredity-specific distress. BC-specific distress (after BC diagnosis) did contribute to both general and heredity-specific distress. This suggests that higher distress scores reflected BC experience, rather than the type of genetic diagnostic procedure. In conclusion, the large majority of BC patients that used DNA-direct reported high satisfaction without increased distress both in the short term, and 1 year after conclusion of genetic testing.

Pancreatic cancer-associated gene polymorphisms in a nation-wide cohort of p16-Leiden germline mutation carriers; a case-control study

Background

The p16-Leiden founder mutation in the CDKN2A gene is the most common cause of Familial Atypical Multiple Mole Melanoma (FAMMM) syndrome in the Netherlands. Individuals with this mutation are at increased risk for developing melanoma of the skin, as well as pancreatic cancer. However, there is a notable interfamilial variability in the occurrence of pancreatic cancer among p16-Leiden families. We aimed to test whether previously identified genetic risk factors for pancreatic cancer modify the risk for pancreatic cancer in p16-Leiden germline mutation carriers.

Methods

Seven pancreatic cancer-associated SNPs were selected from the literature and were genotyped in a cohort of 185 p16-Leiden germline mutation carriers from 88 families, including 50 cases (median age 55 years) with pancreatic cancer and 135 controls (median age 64 years) without pancreatic cancer. Allelic odds ratios per SNP were calculated.

Results

No significant association with pancreatic cancer was found for any of the seven SNPs.

Conclusions

Since genetic modifiers for developing melanoma have already been identified in CDKN2A mutation carriers, this study does not exclude that genetic modifiers do not play a role in the individual pancreatic cancer risk in this cohort of p16-Leiden germline mutation carriers. The search for these modifiers should therefore continue, because they can potentially facilitate more targeted pancreatic surveillance programs.

Lynch syndrome caused by germline PMS2 mutations: delineating the cancer risk

PURPOSE

The clinical consequences of PMS2 germline mutations are poorly understood compared with other Lynch-associated mismatch repair gene (MMR) mutations. The aim of this European cohort study was to define the cancer risk faced by PMS2 mutation carriers.

METHODS

Data were collected from 98 PMS2 families ascertained from family cancer clinics that included a total of 2,548 family members and 377 proven mutation carriers. To adjust for potential ascertainment bias, a modified segregation analysis model was used to calculate colorectal cancer (CRC) and endometrial cancer (EC) risks. Standardized incidence ratios (SIRs) were calculated to estimate risks for other Lynch syndrome-associated cancers.

RESULTS

The cumulative risk (CR) of CRC for male mutation carriers by age 70 years was 19%. The CR among female carriers was 11% for CRC and 12% for EC. The mean age of CRC development was 52 years, and there was a significant difference in mean age of CRC between the probands (mean, 47 years; range, 26 to 68 years) and other family members with a PMS2 mutation (mean, 58 years; range, 31 to 86 years; P < .001). Significant SIRs were observed for cancers of the small bowel, ovaries, breast, and renal pelvis.

CONCLUSION

CRC and EC risks were found to be markedly lower than those previously reported for the other MMR. However, these risks embody the isolated risk of carrying a PMS2 mutation, and it should be noted that we observed a substantial variation in cancer phenotype within and between families, suggesting the influence of genetic modifiers and lifestyle factors on cancer risks.

Can we test for hereditary cancer at 18 years when we start surveillance at 25? Patient reported outcomes

DNA-testing for BRCA1/2 or Lynch syndrome is possible from the age of 18 years, although surveillance usually starts at 25. Some patients regret their decision of testing before age 25. This retrospective study evaluates whether the testing age should be above 25 years to prevent adverse effects such as regret or decisional conflict, by determining the percentage and characteristics of patients reporting these problems. 111 of 219 patients (51%) tested for BRCA1/2 mutations or Lynch syndrome between 18 and 25 years from July 1996 to February 2011, returned self-report surveys. Primary measures were regret, decisional conflict and family influence. Secondary measures included quality of life (QoL), coping style, impact of genetic testing, and risk perception. Median age was 27 [21-40] years, with 86% female. 73% was tested for BRCA1/2, 27% for Lynch syndrome. Only 3% reported regret, however 39% had moderate (32%) to severe (7%) decisional conflict. Regression analysis revealed that decisional conflict was associated with more monitoring/neutral coping style (p < 0.03) or paternal/no family mutation (p < 0.02); there were no differences in QoL, impact or risk perception. 42% were mutation carriers, showing equal decisional conflict to non-carriers. 68% would recommend testing <25 years; 77% desired surveillance <25 years if a mutation carrier. Almost no patient tested for hereditary cancer between 18 and 25 years regretted this decision. A third reported retrospective decisional conflict, especially those actively seeking information when faced with a threat and/or those with a paternal or unknown inheritance. These patients may benefit from decisional support and personalized information.

Evidence for increased SOX3 dosage as a risk factor for X-linked hypopituitarism and neural tube defects

Genomic duplications of varying lengths at Xq26-q27 involving SOX3 have been described in families with X-linked hypopituitarism. Using array-CGH we detected a 1.1 Mb microduplication at Xq27 in a large family with three males suffering from X-linked hypopituitarism. The duplication was mapped from 138.7 to 139.8 Mb, harboring only two annotated genes, SOX3 and ATP11C, and was shown to be a direct tandem copy number gain. Unexpectedly, the microduplication did not fully segregate with the disease in this family suggesting that SOX3 duplications have variable penetrance for X-linked hypopituitarism. In the same family, a female fetus presenting with a neural tube defect was also shown to carry the SOX3 copy number gain. Since we also demonstrated increased SOX3 mRNA levels in amnion cells derived from an unrelated t(X;22)(q27;q11) female fetus with spina bifida, we propose that increased levels of SOX3 could be a risk factor for neural tube defects.

A post-hoc comparison of the utility of sanger sequencing and exome sequencing for the diagnosis of heterogeneous diseases

The advent of massive parallel sequencing is rapidly changing the strategies employed for the genetic diagnosis and research of rare diseases that involve a large number of genes. So far it is not clear whether these approaches perform significantly better than conventional single gene testing as requested by clinicians. The current yield of this traditional diagnostic approach depends on a complex of factors that include gene-specific phenotype traits, and the relative frequency of the involvement of specific genes. To gauge the impact of the paradigm shift that is occurring in molecular diagnostics, we assessed traditional Sanger-based sequencing (in 2011) and exome sequencing followed by targeted bioinformatics analysis (in 2012) for five different conditions that are highly heterogeneous, and for which our center provides molecular diagnosis. We find that exome sequencing has a much higher diagnostic yield than Sanger sequencing for deafness, blindness, mitochondrial disease, and movement disorders. For microsatellite-stable colorectal cancer, this was low under both strategies. Even if all genes that could have been ordered by physicians had been tested, the larger number of genes captured by the exome would still have led to a clearly superior diagnostic yield at a fraction of the cost.

Germline mutations in the spindle assembly checkpoint genes BUB1 and BUB3 are risk factors for colorectal cancer

The spindle assembly checkpoint controls proper chromosome segregation during mitosis and prevents aneuploidy-an important feature of cancer cells. We performed genome-wide and targeted copy number and mutation analyses of germline DNA from 208 patients with familial or early-onset (40 years of age or younger) colorectal cancer; we identified haploinsufficiency or heterozygous mutations in the spindle assembly checkpoint genes BUB1 and BUB3 in 2.9% of them. Besides colorectal cancer, these patients had variegated aneuploidies in multiple tissues and variable dysmorphic features. These results indicate that mutations in BUB1 and BUB3 cause mosaic variegated aneuploidy and increase the risk of colorectal cancer at a young age.

DNA-testing for BRCA1/2 prior to genetic counselling in patients with breast cancer: design of an intervention study, DNA-direct

Background

Current practice for patients with breast cancer referred for genetic counseling, includes face-to-face consultations with a genetic counselor prior to and following DNA-testing. This is based on guidelines regarding Huntington’s disease in anticipation of high psychosocial impact of DNA-testing for mutations in BRCA1/2 genes. The initial consultation covers generic information regarding hereditary breast cancer and the (im)possibilities of DNA-testing, prior to such testing. Patients with breast cancer may see this information as irrelevant or unnecessary because individual genetic advice depends on DNA-test results. Also, verbal information is not always remembered well by patients. A different format for this information prior to DNA-testing is possible: replacing initial face-to-face genetic counseling (DNA-intake procedure) by telephone, written and digital information sent to patients’ homes (DNA-direct procedure).

Methods/design

In this intervention study, 150 patients with breast cancer referred to the department of Clinical Genetics of the Radboud University Nijmegen Medical Centre are given the choice between two procedures, DNA-direct (intervention group) or DNA-intake (usual care, control group). During a triage telephone call, patients are excluded if they have problems with Dutch text, family communication, or of psychological or psychiatric nature. Primary outcome measures are satisfaction and psychological distress. Secondary outcome measures are determinants for the participant’s choice of procedure, waiting and processing times, and family characteristics. Data are collected by self-report questionnaires at baseline and following completion of genetic counseling. A minority of participants will receive an invitation for a 30 min semi-structured telephone interview, e.g. confirmed carriers of a BRCA1/2 mutation, and those who report problems with the procedure.

Discussion

This study compares current practice of an intake consultation (DNA-intake) to a home informational package of telephone, written and digital information (DNA-direct) prior to DNA-testing in patients with breast cancer. The aim is to determine whether DNA-direct is an acceptable procedure for BRCA1/2 testing, in order to provide customized care to patients with breast cancer, cutting down on the period of uncertainty during this diagnostic process.

Trial registration

The study is registered at the Dutch Trial Registry http://www.trialregister.nl (NTR3018).

Clinical phenotype of 5 females with a CDKL5 mutation

Mutations in the X-linked cyclin dependent kinase like 5 (CDKL5) gene have been reported in approximately 80 patients since the first description in 2003. The clinical presentation partly corresponds with Rett syndrome, considering clinical features as intellectual disability, hypotonia, and poor visual, language, and motor development. However, these patients do not meet the consensus criteria for Rett syndrome since they lack the clear period of regression. Furthermore, in contrast to Rett syndrome, patients with CDKL5 mutations, have seizures or infantile spasms starting in the first weeks of life. We present clinical phenotype of 5 girls having a mutation in the CDKL5 gene. All mutations are novel and are pathogenic since they either lead to a frameshift in the reading frame or affect a consensus splice site. Four of the mutations are detected de novo in the affected girl.

Mutation and association analyses of the candidate genes ESR1, ESR2, MAX, PCNA, and KAT2A in patients with unexplained MSH2-deficient tumors

Lynch syndrome (Hereditary non-polyposis colorectal cancer/HNPCC) is a cancer susceptibility syndrome which is caused by germline mutations in DNA mismatch repair (MMR) genes, in particular MLH1 and MSH2. A pathogenic germline mutation in the respective MMR gene is suggested by the finding of a loss of a mismatch repair protein in tumor tissue on immunohistochemical staining combined with an early age of onset and/or the familial occurrence of colorectal cancer. Pathogenic germline mutations are identifiable in around 60% of patients suspected of Lynch syndrome, depending on the familial occurrence. The aim of the present study was to identify novel susceptibility genes for Lynch syndrome. 64 Healthy controls and 64 Lynch syndrome patients with no pathogenic MSH2 mutation but a loss of MSH2 expression in their tumor tissue were screened for rare and disease causing germline mutations in the functional candidate genes ESR1, ESR2, MAX, PCNA, and KAT2A. Thirty variants were identified, and these were then genotyped in an independent sample of 36 mutation negative Lynch syndrome patients and 234 controls. Since a trend towards association was observed for KAT2A, an additional set of 21 tagging SNPs was analyzed at this locus in a final case-control sample of 142 mutation negative Lynch syndrome patients and 298 controls. The mutation analysis failed to reveal any rare disease-causing mutations. No association was found at the single-marker or haplotypic level for any common disease-modifying variant. The present results suggest that neither rare nor common genetic variants in ESR1, ESR2, MAX, PCNA, or KAT2A contribute to the development of Lynch syndrome.

Regular surveillance for Li-Fraumeni Syndrome: advice, adherence and perceived benefits

Li Fraumeni Syndrome (LFS) is a hereditary cancer syndrome characterized by a high risk of developing various types of cancer from birth through late adulthood. Clinical benefits of surveillance for LFS are limited. The aim of this study is to investigate which advice for regular surveillance, if any, is given to high risk LFS individuals, adherence to that advice, and any psychological gain or burden derived from surveillance. Fifty-five high risk individuals (proven carriers and those at 50% risk) from families with a p53 germline mutation were invited to participate, of whom 82% completed a self-report questionnaire assessing advice for regular surveillance, compliance, perceived benefits and barriers of screening and LFS-related distress (IES) and worries (CWS). In total, 71% of the high risk family members received advice to undergo regular surveillance for LFS. The majority (78%) reported adherence with the recommended advice. All high risk women aged 25 or older reported having been advised to undergo annual breast cancer surveillance (n = 11), of whom 64% (n = 7) in specific received advice to undergo a mammography. Seventy-eight percent of respondents indicated having received tailored surveillance advice based on family cancer history. The large majority of respondents believed in the value of surveillance to detect tumors at an early stage (90%) and reported that it gave them a sense of control (84%) and security (70%). Despite its limited clinical benefits, the majority of high risk LFS family are advised to undergo, and are adherent to, and report psychological benefit from, regular surveillance programs.

Distress in partners of individuals diagnosed with or at high risk of developing tumors due to rare hereditary cancer syndromes

OBJECTIVE

Li Fraumeni syndrome (LFS) and Von Hippel-Lindau disease (VHL) are two rare hereditary tumor syndromes, characterized by a high risk of developing multiple tumors at various sites and ages for which preventive and treatment options are limited. For partners, it may be difficult to deal with the on-going threat of tumors in both their spouse and children. Therefore, this study aims to evaluate the prevalence of and factors associated with psychological distress among partners of individuals with or at high risk of LFS or VHL.

METHODS

As part of a nationwide, cross-sectional study, partners of individuals diagnosed with or at high risk of LFS or VHL were invited to complete a self-report questionnaire assessing distress, worries, and health-related quality of life.

RESULTS

Fifty-five (58%) of those high-risk individuals with a partner consented to having their partner approached for the study. In total, 50 partners (91%) completed the questionnaire, of whom 28% reported clinically relevant levels of syndrome-related distress. Levels of distress and worries of the partners and their high-risk spouse were significantly correlated. Younger age and a lack of social support were also associated significantly with heightened levels of distress and worries. The majority of partners (76%) believed that professional psychosocial support should be routinely offered to them.

CONCLUSIONS

Approximately one-quarter of the partners exhibit clinically relevant levels of distress that warrant psychological support. The distress levels of the 'patient' could potentially be used to identify partners at risk of developing clinically relevant levels of distress.

C14ORF179 encoding IFT43 is mutated in Sensenbrenner syndrome

BACKGROUND

Sensenbrenner syndrome is a heterogeneous ciliopathy that is characterised by skeletal and ectodermal anomalies, accompanied by chronic renal failure, heart defects, liver fibrosis and other features.

OBJECTIVE

To identify an additional causative gene in Sensenbrenner syndrome.

METHODS

Single nucleotide polymorphism array analysis and standard sequencing techniques were applied to identify the causative gene. The effect of the identified mutation on protein translation was determined by western blot analysis. Antibodies against intraflagellar transport (IFT) proteins were used in ciliated fibroblast cell lines to investigate the molecular consequences of the mutation on ciliary transport.

RESULTS

Homozygosity mapping and positional candidate gene sequence analysis were performed in two siblings with Sensenbrenner syndrome of a consanguineous Moroccan family. In both siblings, a homozygous mutation in the initiation codon of C14ORF179 was identified. C14ORF179 encodes IFT43, a subunit of the IFT complex A (IFT-A) machinery of primary cilia. Western blots showed that the mutation disturbs translation of IFT43, inducing the initiation of translation of a shorter protein product from a downstream ATG. The IFT-A protein complex is implicated in retrograde ciliary transport along axonemal microtubules. It was shown that in fibroblasts of one of the siblings affected by Sensenbrenner syndrome, disruption of IFT43 disturbs this transport from the ciliary tip to its base. As anterograde transport in the opposite direction apparently remains functional, the IFT complex B proteins accumulate in the ciliary tip. Interestingly, similar results were obtained using fibroblasts from a patient with Sensenbrenner syndrome with mutations in WDR35/IFT121, encoding another IFT-A subunit.

CONCLUSIONS

The results indicate that Sensenbrenner syndrome is caused by disrupted IFT-A-mediated retrograde ciliary transport.

Young age and a positive family history of colorectal cancer are complementary selection criteria for the identification of Lynch syndrome

Families at high risk for Lynch syndrome can effectively be recognised by microsatellite instability (MSI) testing. The aim of the present study is to compare the effectiveness of a MSI test for the identification of Lynch syndrome in patients selected by a pathologist mainly based on young age at diagnosis (MSI-testing-indicated-by-a-Pathologist; MIPA), with that of patients selected by a clinical geneticist mainly based on family history (MSI-testing-indicated-by-Family-History; MIFH). Patients with a Lynch syndrome associated tumour were selected using MIPA (n=362) or MIFH (n=887). Germline DNA mutation testing was performed in 171 out of 215 patients (80%) with a MSI positive tumour. MSI was tested positive in 20% of the MIPA-group group compared to 16% in the MIFH-group (P=0.291). In 91 of 171 patients with MSI positive tumours tested for germline mutations were identified as Lynch syndrome patients: 42% in the MIPA-group and 56% in the MIFH-group (P=0.066). Colorectal cancer (CRC) or endometrial cancer (EC) presenting at an age below 50 years would have led to the diagnosis of Lynch syndrome in 89% of these families (CRC below 50 years: 88% and EC below 50 years: 12%). Families detected by MIPA were characterised more often by extracolonic Lynch syndrome associated malignancies, especially EC (P<0.001). Our results indicate that recognition of Lynch syndrome by CRC or EC below 50 years is as effective as a positive family history. Families from patients selected by individual criteria more often harbour extracolonic Lynch syndrome associated malignancies.

Exome sequencing identifies WDR35 variants involved in Sensenbrenner syndrome

Sensenbrenner syndrome/cranioectodermal dysplasia (CED) is an autosomal-recessive disease that is characterized by craniosynostosis and ectodermal and skeletal abnormalities. We sequenced the exomes of two unrelated CED patients and identified compound heterozygous mutations in WDR35 as the cause of the disease in each of the two patients independently, showing that it is possible to find the causative gene by sequencing the exome of a single sporadic patient. With RT-PCR, we demonstrate that a splice-site mutation in exon 2 of WDR35 alters splicing of RNA on the affected allele, introducing a premature stop codon. WDR35 is homologous to TULP4 (from the Tubby superfamily) and has previously been characterized as an intraflagellar transport component, confirming that Sensenbrenner syndrome is a ciliary disorder.

Genetic Testing in Li-Fraumeni Syndrome: Uptake and Psychosocial Consequences

Purpose

Li-Fraumeni syndrome (LFS) is a hereditary cancer syndrome, characterized by a high risk of developing cancer at various sites and ages. To date, limited clinical benefits of genetic testing for LFS have been demonstrated, and there are concerns about the potential adverse psychosocial impact of genetic testing for LFS. In this study, we evaluated the uptake of genetic testing and the psychosocial impact of undergoing or not undergoing a genetic test for LFS.

Patients and Methods

In total, 18 families with a p53 germline mutation in the Netherlands were identified. Eligible family members were invited to complete a self-report questionnaire assessing motives for undergoing or not undergoing genetic testing, LFS-related distress and worries, and health-related quality of life.

Results

Uptake of presymptomatic testing was 55% (65 of 119). Of the total group, 23% reported clinically relevant levels of LFS-related distress. Carriers were not significantly more distressed than noncarriers or than those with a 50% risk who did not undergo genetic testing. Those with a lack of social support were more prone to report clinically relevant levels of distress (odds ratio, 1.3; 95% CI, 1.0 to 1.5).

Conclusion

Although preventive and treatment options for LFS are limited, more than half of the family members from known LFS families choose to undergo presymptomatic testing. An unfavorable genetic test result, in general, does not cause adverse psychological effects. Nonetheless, it is important to note that a substantial proportion of individuals, irrespective of their carrier status, exhibit clinically relevant levels of distress which warrant psychological support.

Patients with Leber hereditary optic neuropathy fail to compensate impaired oxidative phosphorylation

Ninety-five percent of Leber hereditary optic neuropathy (LHON) patients carry a mutation in one out of three mtDNA-encoded ND subunits of complex I. Penetrance is reduced and more male than female carriers are affected. To assess if a consistent biochemical phenotype is associated with LHON expression, complex I- and complex II-dependent adenosine triphosphate synthesis rates (CI-ATP, CII-ATP) were determined in digitonin-permeabilized peripheral blood mononuclear cells (PBMCs) of thirteen healthy controls and for each primary mutation of a minimum of three unrelated patients and of three unrelated carriers with normal vision and were normalized per mitochondrion (citrate synthase activity) or per cell (protein content). We found that in mitochondria, CI-ATP and CII-ATP were impaired irrespective of the primary LHON mutation and clinical expression. An increase in mitochondrial density per cell compensated for the dysfunctional mitochondria in LHON carriers but was insufficient to result in a normal biochemical phenotype in early-onset LHON patients.

Attitude towards pre-implantation genetic diagnosis for hereditary cancer

The use of pre-implantation genetic diagnosis (PGD) for hereditary cancer is subject to on-going debate, particularly among professionals. This study evaluates the attitude towards PGD and attitude-associated characteristics of those concerned: family members with a hereditary cancer predisposition. Forty-eight Von Hippel-Lindau and 18 Li–Fraumeni Syndrome families were identified via the 9 family cancer clinics in the Netherlands. In total, 216 high risk family members and partners were approached, of whom 179 (83%) completed a self-report questionnaire. Of the high risk family members, 35% expressed a positive attitude towards PGD. Those with a current desire to have children were significantly more likely to have a positive attitude: 48% would consider the use of PGD. No other sociodemographic, medical or psychosocial variables were associated significantly with a positive attitude. The most frequently reported advantage of PGD is the avoidance of a possible pregnancy termination. Uncertainty about late effects was the most frequently reported disadvantage. These results indicate that approximately half of those contemplating a future pregnancy would consider the use of PGD. The actual uptake, however, is expected to be lower. There is no indication that psychosocial factors affect interest in PGD.

Is there alteration in aortic stiffness in Leber hereditary optic neuropathy?

PURPOSE

Leber hereditary optic neuropathy (LHON) is recognized as the most common cause of isolated blindness in young men. The current study was designed to test whether LHON as a mitochondrial disease is associated with vascular functional alterations characterized by aortic elastic properties during echocardiography.

METHODS

A total of 19 patients with typical features of LHON aged 42+/-13 years (10 males) were included. Their results were compared to 19 age- and gender-matched healthy controls. Aortic stiffness index was calculated from the echocardiographically derived aortic diameters and the clinical blood pressure data.

RESULTS

In this patient population, the point mutation was present in 3460G>A position in five cases, in 11778G>A position in five cases, and in 14484T>C position in nine patients. Diastolic aortic diameter (26.0+/-2.5 mm vs 28.4+/-4.1 mm, p<0.05) and aortic stiffness index (5.1+/-2.6 vs 12.0+/-7.9, p<0.05) were significantly increased in LHON patients compared to controls.

CONCLUSIONS

Aortic stiffness can be increased in LHON disease, but further studies are warranted to confirm these findings in a larger LHON patient population with a more reliable method focusing on the pathophysiologic background.

[Two neonates with congenital aniridia: the necessity of genetic investigation]

Two female neonates were diagnosed post partum with bilateral aniridia. The first patient had the familial form, caused by a point mutation in the paired box 6 (PAX6) gene. The second patient had a sporadic aniridia caused by a de novo microdeletion involving both the PAX6 gene as well as the Wilms tumour suppressor-I (WT1) gene. This made screening for the presence of a Wilms tumour necessary. The second patient died several months after birth, due to respiratory insufficiency. Aniridia is a rare developmental disorder of the eye, with absence of most of the iris tissue, caused by an abnormality in the PAX6 gene on chromosome 11p13. Familial aniridia is usually due to a point mutation of the PAX6 gene, which causes solely ocular abnormalities. Sporadic aniridia is caused by a de novo deletion or microdeletion of chromosome 11p13, which affects not only the PAX6 gene but also the adjacent WT1 gene. In these patients, the Wilms tumour, aniridia, genitourinary anomalies, and mental retardation (WAGR) syndrome can be present, and screening for a Wilms tumour is indicated. Unless previous investigation of a family member has demonstrated the WT1 gene to be normal, chromosome studies should always be performed in patients with aniridia.

Clinical expression of Leber hereditary optic neuropathy is affected by the mitochondrial DNA-haplogroup background

Leber hereditary optic neuropathy (LHON) is due primarily to one of three common point mutations of mitochondrial DNA (mtDNA), but the incomplete penetrance implicates additional genetic or environmental factors in the pathophysiology of the disorder. Both the 11778G-->A and 14484T-->C LHON mutations are preferentially found on a specific mtDNA genetic background, but 3460G-->A is not. However, there is no clear evidence that any background influences clinical penetrance in any of these mutations. By studying 3,613 subjects from 159 LHON-affected pedigrees, we show that the risk of visual failure is greater when the 11778G-->A or 14484T-->C mutations are present in specific subgroups of haplogroup J (J2 for 11778G-->A and J1 for 14484T-->C) and when the 3460G-->A mutation is present in haplogroup K. By contrast, the risk of visual failure is significantly less when 11778G-->A occurs in haplogroup H. Substitutions on MTCYB provide an explanation for these findings, which demonstrate that common genetic variants have a marked effect on the expression of an ostensibly monogenic mtDNA disorder.

A simplified and reliable assay for complex I in human blood lymphocytes

Complex I activity of the mitochondrial respiratory chain is difficult to measure in blood lymphocytes because of the limited access of substrates to the enzyme complex in these cells. The results of the present study show that permeabilization of human blood lymphocytes in the presence of protease inhibitors by three cycles of freeze-thawing enables reproducible detection of the rotenone-sensitive complex I activity. To that end, the water-soluble coenzyme Q(10) analogue CoQ(1) and a relatively high concentration of blood lymphocytes were combined in small quartz cuvettes so that the amount of blood needed for this assay remained low. The relationship between the initial rate of NADH oxidation by complex I and the protein concentration was quasi-linear. The fractional inhibition of the total NADH:CoQ(1) oxidoreductase by a saturating concentration of rotenone decreased sharply at CoQ(1) concentrations higher than 20 muM, which is indicative, but does not prove the involvement of a second CoQ(1) binding site at complex I. Since the present complex I assay requires only a small amount of blood, the functionality of this important respiratory chain complex can be assessed in an easy and reliable manner not only in adult patients but also in children suspected to have a mitochondrial disease.

A MELAS-associated ND1 mutation causing leber hereditary optic neuropathy and spastic dystonia

OBJECTIVE

To report a novel mutation that is associated with Leber hereditary optic neuropathy (LHON) within the same family affected by spastic dystonia.

DESIGN

Leber hereditary optic neuropathy is a mitochondrial disorder characterized by isolated central visual loss. Of patients with LHON, 95% carry a mutation in 1 of 3 mitochondrial DNA-encoded complex I genes. The complete mitochondrial DNA was screened for mutations in a patient with LHON without 1 of these 3 primary mutations. The heteroplasmy level and biochemical consequence of the mutation were determined.

RESULTS

A pathogenic 3697G>A/ND1 mutation was detected and seemed associated with an isolated complex I deficiency. This family has similar clinical characteristics as the previously described families with LHON and dystonia with an ND6 mutation.

CONCLUSIONS

The 3697G>A/ND1 mitochondrial DNA mutation causes the LHON and spastic dystonia phenotype in the same family. This mutation can also cause MELAS syndrome (which encompasses mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke), and other genetic factors may contribute to the clinical expression.

Mutations in the ND5 subunit of complex I of the mitochondrial DNA are a frequent cause of oxidative phosphorylation disease

BACKGROUND

Detection of mutations in the mitochondrial DNA (mtDNA) is usually limited to common mutations and the transfer RNA genes. However, mutations in other mtDNA regions can be an important cause of oxidative phosphorylation (OXPHOS) disease as well.

OBJECTIVE

To investigate whether regions in the mtDNA are preferentially mutated in patients with OXPHOS disease.

METHODS

Screening of the mtDNA for heteroplasmic mutations was performed by denaturing high-performance liquid chromatography analysis of 116 patients with OXPHOS disease but without the common mtDNA mutations.

RESULTS

An mtDNA sequence variant was detected in 15 patients, 5 of which were present in the ND5 gene. One sequence variant was new and three were known, one of which was found twice. The novel sequence variant m.13511A-->T occurred in a patient with a Leigh-like syndrome. The known mutation m.13513G-->A, associated with mitochondrial encephalomyopathy lactic acidosis and stroke-like syndrome (MELAS) and MELAS/Leigh/Leber hereditary optic neuropathy overlap syndrome, was found in a relatively low percentage in two patients from two different families, one with a MELAS/Leigh phenotype and one with a MELAS/chronic progressive external ophthalmoplegia phenotype. The known mutation m.13042G-->A, detected previously in a patient with a MELAS/myoclonic epilepsy, ragged red fibres phenotype and in a family with a prevalent ocular phenotype, was now found in a patient with a Leigh-like phenotype. The sequence variant m.12622G-->A was reported once in a control database as a polymorphism, but is reported in this paper as heteroplasmic in three brothers, all with infantile encephalopathy (Leigh syndrome) fatal within the first 15 days of life. Therefore, a causal relationship between the presence of this sequence variant and the onset of mitochondrial disease cannot be entirely excluded at this moment.

CONCLUSIONS

Mutation screening of the ND5 gene is advised for routine diagnostics of patients with OXPHOS disease, especially for those with MELAS- and Leigh-like syndrome with a complex I deficiency.

Influence of mutation type on clinical expression of Leber hereditary optic neuropathy

PURPOSE

The aim of this research was to determine the molecular factors of influence on the clinical expression of Leber hereditary optic neuropathy (LHON), which might aid in counseling LHON patients and families. The prevalence of LHON in the Dutch population was determined.

DESIGN

Observational, retrospective population cohort study.

METHODS

The clinical characteristics of LHON patients of 25 families, previously described in 1963, were reevaluated. The mutation and haplotype were determined in the DNA of one affected LHON patient per family. The genotype of their relatives could be deducted, enabling us to evaluate retrospectively the genotype-phenotype correlation. The prevalence of LHON was determined on the basis of anamnestic evaluation of patients in 1963 and by using population registers of that period.

RESULTS

The LHON mutation does not influence disease penetrance (50% in male subjects; 10% to 20% in female subjects). More than half of the patients with the 14484 mutation exhibit a partial recovery of vision, regardless of the acuteness of disease onset (P = .001), whereas only 22% of the 11778 carriers and 15.4% of the 3460 carriers recovered. The recovery did not take place within the first year after onset and was uncommon after four years. The onset of LHON is in general very acute but might be more gradual in 11778 carriers and in children. The calculated prevalence of LHON in the Dutch population (1/39,000) is very likely an underestimation caused by a selection bias of familial cases in the original study.

CONCLUSIONS

The LHON genotype influences the recovery of vision and disease onset but is unrelated to age, acuteness of onset, or gender. The genotype does not influence disease penetrance. Children might exhibit a slower onset of disease.

Identification of an X-chromosomal locus and haplotype modulating the phenotype of a mitochondrial DNA disorder

Mitochondrial DNA (mtDNA) mutations are a major cause of human disease. A large number of different molecular defects ultimately compromise oxidative phosphorylation, but it is not clear why the same biochemical defect can cause diverse clinical phenotypes. There is emerging evidence that nuclear genes modulate the phenotype of primary mtDNA disorders. Here, we define an X-chromosomal haplotype that interacts with specific MTND mutations to cause visual failure in the most common mtDNA disease, Leber hereditary optic neuropathy. This effect is independent of the mtDNA genetic background and explains the variable penetrance and sex bias that characterizes this disorder.

A patient with a de novo 15q24q26.1 interstitial deletion, developmental delay, mild dysmorphism, and very blue irises

We report on a patient with a de novo 15q24q26.1 interstitial deletion. She presented with developmental delay, behavioral characteristics, and mild dysmorphism with very blue irises. We review the limited literature of interstitial 15q deletions. There was no distinct phenotypic overlap between these two cases in literature and the present patient. Additional reports are necessary in order to establish a possible recognizable deletion 15q24q26.1 phenotype.

Founder mutations among the Dutch

Many genetic disorders demonstrate mutations that can be traced to a founder, sometimes a person who can be identified. These founder mutations have generated considerable interest, because they facilitate studies of prevalence and penetrance and can be used to quantify the degree of homogeneity within a population. This paper reports on founder mutations among the Dutch and relates their occurrence to the history and demography of the Netherlands. International migration, regional and religious endogamy, and rapid population growth played key roles in shaping the Dutch population. In the first millenniums BC and AD, the Netherlands were invaded by Celts, Romans, Huns, and Germans. In more recent times, large numbers of Huguenots and Germans migrated into the Netherlands. Population growth within the Netherlands was slow until the 19th century, when a period of rapid population growth started. Today, the Dutch population numbers 16 million inhabitants. Several different classes of founder mutations have been identified among the Dutch. Some mutations occur among people who represent genetic isolates within this country. These include mutations for benign familial cholestasis, diabetes mellitus, type I, infantile neuronal ceroid lipofuscinosis, L-DOPA responsive dystonia, and triphalangeal thumb. Although not related to a specific isolate, other founder mutations were identified only within the Netherlands, including those predisposing for hereditary breast-ovarian cancer, familial hypercholesterolemia, frontotemporal dementia, hereditary paragangliomas, juvenile neuronal ceroid lipofuscinosis, malignant melanoma, protein C deficiency, and San Filippo disease. Many of these show a regional distribution, suggesting dissemination from a founder. Some mutations that occur among the Dutch are shared with other European populations and others have been transmitted by Dutch émigrés to their descendents in North America and South Africa. The occurrence of short chromosomal regions that have remained identical by descent has resulted in relatively limited genetic heterogeneity for many genetic conditions among the Dutch. These observations demonstrate the opportunity for gene discovery for other diseases and traits in the Netherlands.

A 2-bp deletion in theGJA1 gene is associated with oculo-dento-digital dysplasia with palmoplantar keratoderma

Oculo-dento-digital dysplasia (ODDD, OMIM no. 164210) is a pleiotropic disorder characterized mainly by ocular anomalies, varying degrees of finger and toe syndactyly, and enamel defects. It is caused by missense mutations in the gene coding for the gap junction protein connexin 43 or GJA1. Other types of mutations have so far not been reported. Here we describe a Dutch kindred with ODDD showing a new symptom, palmoplantar keratoderma, and associated with a novel 2-bp deletion mutation of GJA1. The dinucleotide deletion 780_781delTG is located in the cytoplasmic C-terminal loop and leads to a frameshift. This is predicted to lead to the production of a slightly truncated protein with 46 incorrect amino acids in the C-terminal cytoplasmic loop (C260fsX307). This novel mutation may explain the presence of skin symptoms.

A patient with a de novo 11q24.2-->qter deletion

In the group of patients with terminal 11q deletion reported up to now. Jacobson syndrome has been delineated as a distinct clinical entity. In the present report we describe the clinical findings in a 3-year old girl with de novo deletion 11q24.2-->11qter, and compare the findings with Jacobson syndrome.

Sequence analysis of the mitochondrial genomes from Dutch pedigrees with Leber hereditary optic neuropathy

The complete mitochondrial DNA (mtDNA) sequences for 63 Dutch pedigrees with Leber hereditary optic neuropathy (LHON) were determined, 56 of which carried one of the classic LHON mutations at nucleotide (nt) 3460, 11778, or 14484. Analysis of these sequences indicated that there were several instances in which the mtDNAs were either identical or related by descent. The most striking example was a haplogroup J mtDNA that carried the 14484 LHON mutation. Four different but related mitochondrial genotypes were identified in seven of the Dutch pedigrees with LHON, including six of those described by van Senus. The control region of the founder sequence for these Dutch pedigrees with LHON matches the control-region sequence that Macmillan and colleagues identified in the founder mtDNA of French Canadian pedigrees with LHON. In addition, we obtained a perfect match between the Dutch 14484 founder sequence and the complete mtDNA sequences of two Canadian pedigrees with LHON. Those results indicate that these Dutch and French Canadian 14484 pedigrees with LHON share a common ancestor, that the single origin of the 14484 mutation in this megalineage occurred before the year 1600, and that there is a 14484/haplogroup J founder effect. We estimate that this lineage--including the 14484 LHON mutation--arose 900-1,800 years ago. Overall, the phylogenetic analyses of these mtDNA sequences conservatively indicate that a LHON mutation has arisen at least 42 times in the Dutch population. Finally, analysis of the mtDNA sequences from those pedigrees that did not carry classic LHON mutations suggested candidate pathogenic mutations at nts 9804, 13051, and 14325.

VATER--tibia aplasia association: report on two patients

We report two patients with oesophageal atresia, tracheo-oesophageal fistula and unilateral tibial aplasia. The karyotype in both patients was normal and both cases were sporadic. The congenital defects of the children can be regarded as an uncommon variant of VA(C)TER(L) association. Recently Basel and Goldblatt [(2000) Clin Dysmorphol 9:205-208] reported a similar patient with a VATER-tibia aplasia association.

The otolaryngological manifestations of mitochondrial disease and the risk of neurodegeneration with infection

OBJECTIVE

To report the nature and extent of hearing loss and other otolaryngological problems in patients with mitochondrial disease, and to document the risk of neurodegeneration with infection.

DESIGN

Medical chart review and telephone interview of 40 patients with documented mitochondrial disease.

SETTING

An international referral center for the diagnosis and management of mitochondrial disorders.

PATIENTS

We describe 40 patients with a definitive diagnosis of mitochondrial disease. Thirty-three (82%) were younger than 15 years.

RESULTS

Hearing loss was the most common clinical finding associated with mitochondrial disease. Twenty-eight (80%) of the 35 patients undergoing testing had hearing loss or significant auditory dysfunction. In 20 (57%) of these, brainstem conduction abnormalities were identified. Eight (30%) of the 27 patients had an abnormal number of recurrent upper respiratory tract infections, and 4 (50%) of these had life-threatening or neurodegenerative sequelae. Mitochondrial disease followed an episodic course, with periods of stasis or slow developmental progress, punctuated by neurodegenerative events in 18 (60%) of 30 patients. Intercurrent infection was recognized as a precipitant of neurodegenerative events in 13 (72%) of 18 patients with a history of episodic degeneration.

CONCLUSIONS

Children and adults with mitochondrial disorders are at high risk for hearing loss and life-threatening complications of intercurrent infections. A constellation of audiologic abnormalities, multiorgan system involvement, and history of neuromuscular setbacks with infection strongly suggests mitochondrial disease. Knowledge of these features can lead to more rapid diagnosis and improved medical and surgical management for this special group of patients with fundamental defects in bioenergy metabolism.