Prenatal testing for Huntington's disease in the Netherlands from 1998 to 2008.

This study aims to give an overview of the number of prenatal tests for Huntington's disease (HD), test results, and pregnancy outcomes in the Netherlands between 1998 and 2008 and to compare them with available data from the period 1987 to 1997. A total of 126 couples underwent prenatal diagnosis (PND) on 216 foetuses: 185 (86%) direct tests and 31 (14%) exclusion tests. In 9% of direct tests the risk for the foetus was 25%. Four at-risk parents (4%) carried intermediate alleles. Ninety-one foetuses had CAG expansions ≥36% or 50% risk haplotypes: 75 (82%) were terminated for HD, 12 (13%) were carried to term; four pregnancies were miscarried, terminated for other reasons or lost to follow-up. Unaffected pregnancies (122 foetuses) resulted in the birth of 112 children. The estimated uptake of PND was 22% of CAG expansion carriers (≥36 repeats) at reproductive age. PND was used by two new subgroups: carriers of intermediate alleles and 50% at-risk persons opting for a direct prenatal test of the foetus. A significant number of HD expansion or 50% risk pregnancies were continued. Speculations were made on causative factors contributing to these continuations. Further research on these couples' motives is needed.

Neonatal onset autosomal dominant polycystic kidney disease (ADPKD) in a patient homozygous for a PKD2 missense mutation due to uniparental disomy.

Autosomal dominant polycystic kidney disease (ADPKD), due to a heterozygous mutation in PKD1 or PKD2, is usually an adult onset disease. Renal cystic disease is generally milder in PKD2 patients than in PKD1 patients. Recently, several PKD1 patients with a severe renal cystic phenotype due to a second modifying PKD1 allele, or carrying two incomplete penetrant PKD1 alleles, have been described. This study reports for the first time a patient with neonatal onset of PKD homozygous for an incomplete penetrant PKD2 missense variant due to uniparental disomy.

Hepatocyte nuclear factor (HNF)1A and HNF4A substitution occurring simultaneously in a family with maturity-onset diabetes of the young.

INTRODUCTION: Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes mellitus characterized by an early age at onset, autosomal dominant inheritance and a primary defect in the function of the B-cells of the pancreas. We report a family with two members carrying a substitution in both the hepatocyte nuclear factor (HNF)1A and HNF4A gene simultaneously. CASE REPORT: A 39-year-old man was referred because of mild diabetic retinopathy. Because of a dominant presentation of diabetes in his family, genetic testing was performed. Sequence analysis of the genes involved in MODY-1-3 revealed the presence of an amino acid substitution in the HNF1A as well as the HNF4A gene. Both substitutions were also detected in his mother. The HNF1A substitution has been described previously as pathogenic, whereas the HNF4A substitution had not been found previously. The HNF4A substitution was located in a conserved region of the protein and, additionally, the proband and his mother had high birthweights and low triglyceride levels, both of which are associated with pathogenic HNF4A substitutions. CONCLUSIONS: To our knowledge this is the first reported family carrying both a substitution of HNF1A and HNF4A gene simultaneously. The exact contribution of each substitution to the phenotype of our subjects remains to be further elucidated, however, given the high birthweights and the low triglyceride levels in those with both substitutions, it is reasonable that the HNF4A substitution is pathogenic.

Reduced penetrance alleles for Huntington's disease: a multi-centre direct observational study.

OBJECTIVE: To obtain penetrance data for Huntington's disease when DNA results are in the range of 36-39 CAG repeats and assess the consistency of reporting the upper allele from two reference centres. METHOD: Data were collected anonymously on age of onset or age last known to be unaffected from a cohort of individuals with results in this range. DNA samples were re-analysed in two reference centres. Kaplan-Meier analysis was used to construct an age of onset curve and penetrance figures. RESULTS: Clinical data and concordant DNA results from both reference centres were available for 176 samples; penetrance figures (and 95% confidence intervals) for this cohort, at age 65 and 75 years, were 63.9% (55.5% to 73.2%) and 74.2% (64.2% to 84.2%), respectively. Inclusion of 28 additional subjects for whom repeat DNA results were unavailable, obtained from only one reference centre, or discrepant by one repeat within this range, gave penetrance data (including 95% confidence intervals) at ages 65 and 75 years of 62.4% (54.4% to 70.4%) and 72.7.% (63.3% to 82.1%), respectively. 238 duplicate results were available from the reference centres; 10 (4.2%) differed by one CAG repeat in the reporting of the upper allele and in two (0.84%) of these cases the discrepancy was between 39 and 40 repeats. CONCLUSION: When DNA results are in this range, a conservative approach is to say that there is at least a 40% chance the person will be asymptomatic at age 65 years and at least a 30% chance the person will be asymptomatic at age 75 years.

Juvenile-onset neuronal ceroid lipofuscinosis with infantile CLN1 mutation and palmitoyl-protein thioesterase deficiency.

Accurate diagnosis, especially in progressive hereditary diseases, is essential for the treatment and genetic counseling of the patient and the family. Neuronal ceroid lipofuscinoses (NCL) are amongst the most common groups of neurodegenerative diseases. Infantile, juvenile, and adult-onset types with multiple genotype-phenotype associations have been described. A fluorimetric enzyme assay for palmitoyl protein thioesterase (PPT) from leukocytes and fibroblasts has been previously developed to confirm the diagnosis of infantile NCL. We describe a patient with juvenile-onset NCL phenotype with a new CLN1 mutation and deficient PPT activity. Over 40 different mutations have been found in patients with PPT deficiency, indicating that screening for known mutations is not an efficient way to diagnose this disorder. Therefore, PPT enzyme analysis should precede mutation analysis in suspected PPT deficiency, particularly in patients with granular osmiophilic deposits (GROD) or in patients who have negative ultrastructural data. The use of enzyme assay led to the diagnosis of this patient with juvenile-onset Finnish variant NCL with PPT deficiency, and we expect that greater awareness of the utility of the enzymatic assay may lead to identification of other similar cases awaiting a definitive diagnosis.

Maturity onset diabetes of the young: Seek and you will find.

Maturity onset diabetes of the young (MODY) is a monogenic, autosomal dominant form of diabetes characterised by mutations in genes resulting in dysfunction of pancreatic ß-cells and subsequent insulin production. We present a family with HNF1A-MODY due to a likely pathogenic mutation in HNF1A (c.59G>A, p.Gly20Glu), diagnosed a long time after the first diagnosis of diabetes. Currently 13 MODY subtypes caused by mutations in 13 genes, are known. We describe the four most prevalent forms in more detail, i.e. HNF4A-MODY, GCK-MODY, HNF1A-MODY and HNF1B-MODY, together responsible for probably 99% of MODY cases. The different forms of MODY vary in prevalence, severity of diabetes, occurrence and severity of diabetic complications and response to treatment. New tools, such as the MODY probability calculator, may be of assistance in finding those patients in whom further genetic testing for possible MODY is warranted. However, as our described family shows, a doctor's clinical eye and taking the time for a detailed family history may be equal to, or even better than, the best prediction rule.

IGSF1 Deficiency: Lessons From an Extensive Case Series and Recommendations for Clinical Management.

CONTEXT: Mutations in the immunoglobulin superfamily, member 1 (IGSF1) gene cause the X-linked IGSF1 deficiency syndrome consisting of central hypothyroidism, delayed pubertal testosterone rise, adult macroorchidism, variable prolactin deficiency, and occasionally transient partial GH deficiency. Since our first reports, we discovered 20 new families with 18 new pathogenic IGSF1 mutations. OBJECTIVE: We aimed to share data on the largest cohort of patients with IGSF1 deficiency to date and formulate recommendations for clinical management. METHODS: We collected clinical and biochemical characteristics of 69 male patients (35 children, 34 adults) and 56 female IGSF1 mutation carriers (three children, 53 adults) from 30 unrelated families according to a standardized clinical protocol. At evaluation, boys were treated with levothyroxine in 89%, adult males in 44%, and females in 5% of cases. RESULTS: Additional symptoms in male patients included small thyroid gland volume (74%), high birth weight (25%), and large head circumference (20%). In general, the timing of pubertal testicular growth was normal or even premature, in contrast to a late rise in T levels. Late adrenarche was observed in patients with prolactin deficiency, and adult dehydroepiandrosterone concentrations were decreased in 40%. Hypocortisolism was observed in 6 of 28 evaluated newborns, although cortisol concentrations were normal later. Waist circumference of male patients was increased in 60%, but blood lipids were normal. Female carriers showed low free T4 (FT4) and low-normal FT4 in 18% and 60%, respectively, delayed age at menarche in 31%, mild prolactin deficiency in 22%, increased waist circumference in 57%, and a negative correlation between FT4 concentrations and metabolic parameters. CONCLUSION: IGSF1 deficiency represents the most common genetic cause of central hypothyroidism and is associated with multiple other characteristics. Based on these results, we provide recommendations for mutational analysis, endocrine work-up, and long-term care.

Novel transforming sequences in human acute myelocytic leukemia cell lines.

DNA transfection analyses using the tumorigenicity assay were performed on seven human acute myelocytic leukemia (AML) cell lines. DNAs from all cell lines induced tumors in nude mice. Respective transforming sequences could be identified as activated N-ras genes in AML cell lines THP-1, KG-1 and Rc2a. We observed the transfer of five putative novel transforming sequences from DNAs of cell lines U937, ML-1, HEL and CTV-2. These sequences appear to be unrelated to each other and previously known oncogenes. Transfections containing these transforming genes show distinctive biological and morphological characteristics. Our data suggest that the transforming sequences reported here became activated during the transfection process rather than the AML cell line.

Increased prevalence of catecholamine excess and phaeochromocytomas in a well-defined Dutch population with SDHD-linked head and neck paragangliomas.

OBJECTIVE: The aim of this study was to identify the prevalence of catecholamine excess and phaeochromocytomas in a well-defined population of people with hereditary head and neck paragangliomas. METHODS: We studied in a prospective follow-up protocol all consecutive patients referred to the Department of Endocrinology, Leiden University Medical Center, Leiden, The Netherlands with documented head and neck paragangliomas and either a positive family history for paragangliomas or a proven SDHD gene mutation. Initial analysis included medical history, physical examination and the measurement of excretion of catecholamines in two 24-h urine collections. In the case of documented catecholamine excess iodinated meta-iodobenzylguanidine (123I-MIBG) scintigraphy and magnetic resonance imaging were done. RESULTS: Between 1988 and 2003, 40 consecutive patients (20 male and 20 female) with documented head and neck paragangliomas were screened. Biochemical screening revealed urinary catecholamine excess in 15 patients (37.5%). In nine of these 15 patients a lesion was found by 123I-MIBG scintigraphy. Exact localization by magnetic resonance imaging revealed phaeochromocytomas in seven of the 15 patients. One of the nine patients had an extra-adrenal paraganglioma. Histopathological examination in a subset of tumors displayed loss of heterozygosity of the wild-type SDHD allele in all cases. CONCLUSIONS: The prevalence of catecholamine excess (37.5%) and phaeochromocytomas (20.0%) is high in patients with familial head and neck paragangliomas. Therefore, patients with hereditary head and neck paragangliomas require lifelong follow up by biochemical testing for catecholamine excess.

[From gene to disease; from CLN1, CLN2 and CLN3 to neuronal ceroid lipofuscinosis]. / Van gen naar ziekte; van Clni, CLN2 en CLN3 naar neuronale ceroidlipofuscinose.

The neuronal ceroid lipofuscinoses (NCL) are worldwide the most common lysosomal storage disorders of childhood. Clinical features often include progressive visual impairment, seizures, psychomotor deterioration, dementia, and premature death. Most NCL cases are caused by mutations in the CLN1, CLN2 and CLN3 genes, which play an essential role in lysosomal protein degradation. Laboratory diagnostics for a patient suspected of NCL should start with enzyme analysis in the case of INCL and LINCL and investigation of lymphocyte vacuolisation for JNCL. Diagnosis at the protein level is not available for JNCL, but CLN3 mutation analysis is possible. The carrier status of healthy relatives in families with known mutations in either CLN1, CLN2, CLN3 or CLN6 can be determined with certainty by mutation analysis.

[Molecular diagnosis on indication of maturity onset diabetes of the young; results from 184 patients]. / Moleculaire diagnostiek bij aanwijzingen voor 'maturity onset diabetes of the young'; resultaten bij 184 patiënten.

OBJECTIVE: To describe the results of mutation analysis of the genes involved in maturity onset diabetes of the young (MODY) types 1-3. DESIGN: Descriptive. METHOD: In the period July 2000-October 2003 the DNA from 184 possible MODY patients was analysed for the presence of mutations of the genes involved in MODY types 1, 2 and 3. The patients fulfilled at least one of the following criteria: diabetes mellitus had been diagnosed before the age of 25, or at least before the age of 40, there was a family history of diabetes mellitus at an early age, there were no characteristics to indicate diabetes mellitus type 1 or 2. RESULTS: In the blood of 65 patients (35%) a pathogenic gene mutation was found. A total of 45 patients had a mutation in the HNF-1alpha-gene (which is linked to MODY3), 11 in the glucokinase gene (MODY2) and 9 in the HNF-4alpha-gene (MODY1). Of all the HNF-1alpha-gene mutations, the insertion of a C in codon 291 was the most frequently seen (in 11 families). A mutation in exon 9 of the HNF-1alpha-gene was also shown in 9 apparently non-related families, which probably was a founder mutation. CONCLUSION: The MODY subtype was found in one third of the selected patients. This diagnosis may have implications in the clinical management of the patient.

[From gene to disease; PKHD1 and recessive polycystic kidney disease]. / Van gen naar ziekte; PKHD1 en recessief erfelijke cystennieren.

Autosomal recessive polycystic kidney disease (ARPKD) is a severe form of polycystic kidney disease characterised by enlarged kidneys and congenital hepatic fibrosis. The disease has an incidence of 1:7000-:20,000 and is caused by mutations in the PKHD1 gene, which under normal conditions produces the protein fibrocystin, also named polyductin. This protein may be a transmembrane receptor or ligand that plays a role in collecting duct and biliary differentiation. The major site of expression is the primary cilium, and in particular the basal body of the cilium, underlining a link between aberrant cilial function and cystogenesis. Prenatal diagnostics is possible using DNA analysis or ultrasonography.

The growth response to GH treatment is greater in patients with SHOX enhancer deletions compared to SHOX defects.

OBJECTIVE: Short stature caused by point mutations or deletions of the short stature homeobox (SHOX) gene (SHOX haploinsufficiency (SHI)) is a registered indication for GH treatment. Patients with a SHOX enhancer deletion (SED) have a similar phenotype, but their response to GH is unknown. It is uncertain if duplications of SHOX or its enhancer (SDUP) cause short stature. This study aimed to describe the clinical characteristics and growth response to GH treatment in patients with aberrations of SHOX and its enhancers. DESIGN: In this retrospective multi-center study (2002-March 2014) clinical information was available from 130 patients (72 SHI, 44 SED, and 14 SDUP) of whom 52 patients were treated with GH. We evaluated height, sitting height (SH), arm span, dysmorphic features and indicators of the growth response to GH (delta height SDS, height velocity, and index of responsiveness). RESULTS: Patients with SEDs showed similar HtSDS to patients with SHI (-2.3 and -2.6, respectively, P=0.2), but they were less disproportionate (SH/height ratio SDS 2.0 vs 3.1 (P<0.01) and extremities/trunk ratio 2.57 vs 2.43 (P=0.03)). The 1st year growth response to GH treatment was significantly greater in prepubertal patients with SEDs than SHI. None of the patients with an SDUP was disproportionate and SDUP cosegregated poorly with short stature; their growth response to GH treatment (n=3) was similar to the other groups. CONCLUSIONS: Patients with SEDs are equally short, but less disproportionate than patients with SHI, and show a greater response to GH.

A European pilot quality assessment scheme for molecular diagnosis of Huntington's disease.

This paper reports a European pilot External Quality Assessment (EQA) scheme for the molecular diagnosis of Huntington's disease (HD). The European Molecular Genetics Quality Network (EMQN) chose HD as a relatively simple assay that allows a range of difficulty in terms of technical competence and interpretation. Fourteen centres from 12 different countries participated. The scheme organiser provided five cases together with mock clinical information. The participating laboratories were asked to complete the analyses and return the reports in English to their normal laboratory format within a fixed period. The scheme demonstrates a level of potential misdiagnosis in molecular analysis of HD as well as a wide variety in way of reporting laboratory results. Overall 9/146 (6.2%) of alleles fell outside the set limits, and the rate of misdiagnosis was 1/78 (1.3%). A closer estimate of diagnostic accuracy will require expansion of the scheme.

Using a roster and haplotyping is useful in risk assessment for persons with intermediate and reduced penetrance alleles in Huntington disease.

The risk of a person having a child with an inherited disorder, caused by an unstable triplet repeat, such as Huntington disease (HD), depends on the expansion of the mutation in that person, which is connected both to the biological nature of the mutation and to the person's relation to the carrier of the full mutation. Once the mutation causing HD was identified, we were able to diagnose sporadic patients. A sporadic patient can sometimes be connected to a known HD pedigree by using a roster. By haplotyping and calculating the posterior identity-by-descent probability, we could establish whether a connection was coincidental or not. Furthermore, we describe the frequency of intermediate and reduced penetrance alleles detected. Using the family history and the roster to search for a connection, we examined whether these alleles were on the HD haplotype of a family. It is important to know the origin of an intermediate or reduced penetrance allele because if it comes from an HD branch of the family or from the non-HD affected side of the pedigree, different risks for relatives and penetrance ensue. In our study, most intermediate alleles came from the non-HD-affected side of the pedigree and had a repeat size in the lower range with a negligible risk for expansion. Intermediate alleles on the HD haplotypes were larger and found in predictive test applicants from known families or relatives from new mutations with a higher risk for expansion. Reduced penetrance alleles in the higher range were mainly found in symptomatic and predictive test applicants from known families, with a considerable risk for penetrance, although at older age. We conclude that a roster, a thorough family history, and haplotyping in persons with intermediate and reduced penetrance alleles are essential in considering the risk of a person having (a child with) HD.

Predictive testing of 25 percent at-risk individuals for Huntington disease (1987-1997).

Before the mutation causing Huntington disease was identified, predictive testing of 25% at-risk persons with a 50% at-risk parent who did not wish to know his/her genetic status, was only possible by exclusion testing. The exclusion test, using linked markers, ensures the parent's wish not to know because the parent's risk is not changed. When mutation analysis became available in 1993, new testing options for 25% at-risk persons emerged: viz., the exclusion-definitive test and direct mutation analysis. These new tests not only disclose the risk of the test candidate, but may also change the risk of the at-risk parent and siblings. The testing options for 25% at-risk test applicants and their consequences are discussed and the testing procedures and results of testing 64 25% at-risk persons in the period 1987 to 1997 are described. Relatives received unsought information in 56% of the test procedures before and 34% after the mutation was identified. A decision tree and guidelines for predictive testing of 25% at-risk test applicants are proposed. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:662-668, 1999.

Detection of K-ras mutations by denaturing gradient gel electrophoresis (DGGE): a study on pancreatic cancer.

In pancreatic neoplasias mutations in the first exon (codon 12) of K-ras gene occur at high frequency and seem to have a diagnostic significance. We set up the DGGE conditions to search for these mutations in pancreatic tumor sample DNAs. All samples were directly classified by simply comparing their DGGE patterns with those of control cell lines carrying known K-ras base substitutions. We found a mutation frequency of 73% in pancreatic adenocarcinoma, whereas no mutations were observed in benign lesions. The non-isotopic method we used turned out to be rapid and sensitive. DGGE could therefore be utilized for the detection of K-ras mutations in pancreatic lesions, to evaluate their actual or potential malignancy. In general, DGGE could be useful for K-ras gene screening on pathological tissue samples.

[From gene to disease; 'maturity-onset diabetes of the young' (MODY), monogenetic inheritable forms of diabetes mellitus]. / Van gen naar ziekte; 'maturity-onset diabetes of the young' (MODY), monogenetisch overervende vormen van diabetes mellitus.

Maturity-onset diabetes of the young (MODY) exhibits an autosomal dominant pattern of inheritance and can be divided in at least five subtypes (MODY 1 to 5), each subtype being caused by mutations in a specific gene. The unambiguous molecular diagnosis of the specific MODY subtype facilitates an early diagnosis of diabetes and can help to reduce the development of diabetic complications. Furthermore, MODY2 patients generally have a milder clinical course and fewer complications than MODY3 patients, who consequently require a more aggressive therapeutic approach.

[From gene to disease; achondroplasia and other skeletal dysplasias due to an activating mutation in the fibroblast growth factor]. / Van gen naar ziekte; achondroplasie en andere skeletdysplasieën door een activerende mutatie in een receptor voor fibroblastgroeifactor.

Achondroplasia, the most common and best known skeletal dysplasia, is inherited in an autosomal dominant fashion. Like a number of other skeletal dysplasias, among which hypochondroplasia and thanatophoric dysplasia, achondroplasia is caused by mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. FGFR3 is a negative regulator of bone growth. Binding of fibroblast growth factors to the FGFR3 receptor stimulates its tyrosine kinase activity in the cell. This activates a signal transduction pathway that regulates enchondral ossification by inhibition of cell division and stimulation of cell maturation and differentiation. Mutations in the FGFR3 gene give rise to activation of the receptor in the absence of growth factors, thus causing abnormal long bone development. Position and type of mutation in the FGFR3 gene determine the extent of overactivation and thus the severity of the skeletal abnormality.

[From gene to disease; HD gene and Huntington disease]. / Van gen naar ziekte; het HD-gen en de ziekte van Huntington.

Huntington's disease (HD) is a late onset, incurable, autosomal dominantly-inherited, progressive neuropsychiatric disease, characterised by chorea, changes in personality, mood and behaviour, and dementia. Huntington's disease is a clinical diagnosis. The advent of DNA diagnosis has made predictive, prenatal and preimplantation testing possible for at-risk persons or asymptomatic carriers. The prevalence is estimated to be 3-10/100,000 among individuals of European descent; HD is less common in other ethnic groups. Huntington's disease is caused by an expanded trinucleotide CAG repeat in the HD gene on chromosome 4. The gene encodes for the protein huntingtin, with an as yet unknown function. The mutated huntingtin has an elongated stretch of glutamines which leads to a gain of function such as overactivity, excitotoxicity, or to interactions with other proteins.