Molecular analysis of two novel missense mutations in the GDF5 proregion that reduce protein activity and are associated with brachydactyly type C.

Growth and differentiation factor 5 (GDF5) plays a central role in bone and cartilage development by regulating the proliferation and differentiation of chondrogenic tissue. GDF5 is synthesized as a preproprotein. The biological function of the proregion comprising 354 residues is undefined. We identified two families with a heterozygosity for the novel missense mutations p.T201P or p.L263P located in the proregion of GDF5. The patients presented with dominant brachydactyly type C characterized by the shortening of skeletal elements in the distal extremities. Both mutations gave rise to decreased biological activity in in vitro analyses. The variants reduced the GDF5-induced activation of SMAD signaling by the GDF5 receptors BMPR1A and BMPR1B. Ectopic expression in micromass cultures yielded relatively low protein levels of the variants and showed diminished chondrogenic activity as compared to wild-type GDF5. Interestingly, stimulation of micromass cells with recombinant human proGDF5(T201P) and proGDF5(L263P) revealed their reduced chondrogenic potential compared to the wild-type protein. Limited proteolysis of the mutant recombinant proproteins resulted in a fragment pattern profoundly different from wild-type proGDF5. Modeling of a part of the GDF5 proregion into the known three-dimensional structure of TGFß1 latency-associated peptide revealed that the homologous positions of both mutations are conserved regions that may be important for the folding of the mature protein or the assembly of dimeric protein complexes. We hypothesize that the missense mutations p.T201P and p.L263P interfere with the protein structure and thereby reduce the amount of fully processed, biologically active GDF5, finally causing the clinical loss of function phenotype.

Translation of a research-based genetic test on a rare syndrome into clinical service testing, with sotos syndrome as an example.

BACKGROUND AND AIMS: It is often the case that the genetic background of a rare disease has been solved, but the testing of a clinical patient can be performed only through research projects. Translating a research-based test into diagnostic service may also appear laborious and costly. Based on our molecular research of the genetics of Sotos syndrome, we developed a clinical laboratory test that is both effective and relatively inexpensive. METHODS AND RESULTS: Pilot testing was performed with samples of clinically diagnosed Sotos cases (n=13), and testing was continued with samples of patients who were suspected of having Sotos syndrome (n=161). The testing methods used were direct sequencing and multiplex ligation-dependent probe amplification. Sotos syndrome was a suitable example for test translation, because its genetic background was well established, and the demand for the test was expected to be fairly high. In the pilot phase, a mutation was detected in 12 out of 13 patients (92%), and in the second group, 49 out of 161 (30%) patients had a mutation in the NSD1 gene. CONCLUSIONS: In Sotos syndrome, detecting the mutation is valuable for the patient/family, while the value of a negative result is less clear and other differential diagnostic diagnoses should be considered. For successful translation of the research-based test into routine diagnostics, intense collaboration between clinicians, researchers, and diagnostic laboratory personnel is essential.

[Fabry disease]. / Fabryn tauti.

Fabry disease is an X-linked inherited condition with the absence or reduction of alpha-galactosidase A- activity in lysosomes leading to accumulation of globotriaosylceramide and related neutral glycosphingolipids. Manifestations of Fabry disease include progressive renal and cardiac insufficiency, neuropathic pain, gastrointestinal symptoms, cerebral infarction and skin and pulmonary symptoms. First symptoms of Fabry disease usually appear in childhood. The symptoms in females may be as severe as in males. Early diagnosis of Fabry disease is important because enzyme replacement therapy can stabilize the condition and prevent progression of the disease.

Terminal 3p deletions in two families--correlation between molecular karyotype and phenotype.

The 3p deletion syndrome is a rare disorder caused by deletions of different sizes in the 3p25-pter region. It is characterized by growth retardation, developmental delay, mental retardation, dysmorphism, microcephaly, and ptosis. The phenotype of individuals with deletions varies from normal to severe. Most cases occur de novo, but a few familial cases have been reported. We describe two families with terminal 3p deletions and extremely variable clinical features. In family A, the mother and daughter were extremely mildly affected whereas the son had more severe clinical features. In family B, the mother was normal and her son was affected, having some symptoms that had not been described in the 3p deletion syndrome before. The deletions were characterized by genome-wide SNP array analysis and were 9 and 1.1 Mb in size. Sequencing analysis of the CHL1, CNTN4, and CRBN genes did not reveal any masked recessive alleles that might explain the more severe phenotypes in the probands. In family A, the 9 Mb deletion can be considered causal for the 3p deletion syndrome in the proband, but the extremely mild phenotype in the other family members remains unexplained. In family B, the 1.1 Mb terminal deletion encompasses only the CHL1 gene, which is insufficient to cause 3p deletion symptoms; thus the clinical features observed in this family may have a different cause. The variable penetrance of 3p deletions creates challenges in genetic counseling, as the phenotype of the offspring cannot be predicted based on chromosomal and/or genome-wide array analytical findings.

Genitopatellar syndrome in an adolescent female with severe osteoporosis and endocrine abnormalities.

Genitopatellar syndrome (GPS) is a rare disorder with characteristic craniofacial features, congenital flexion contractures of the lower limbs, absent or abnormal patellae, urogenital anomalies, and severe psychomotor retardation. Twelve patients with ages from 15 days to 12 years and two affected fetuses have been reported. We describe a 17-year-old female with a phenotype consistent with GPS. Being the oldest reported patient, she is the first one showing severe symptomatic osteoporosis and endocrine abnormalities including primary hypothyroidism and delayed puberty. We suggest that these novel findings are also manifestations of GPS.

Missense mutations to the TSC1 gene cause tuberous sclerosis complex.

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterised by the development of hamartomas in a variety of organs and tissues. The disease is caused by mutations in either the TSC1 gene on chromosome 9q34 or the TSC2 gene on chromosome 16p13.3. The TSC1 and TSC2 gene products, TSC1 and TSC2, interact to form a protein complex that inhibits signal transduction to the downstream effectors of the mammalian target of rapamycin (mTOR). Here we investigate the effects of putative TSC1 missense mutations identified in individuals with signs and/or symptoms of TSC on TSC1-TSC2 complex formation and mTOR signalling. We show that specific amino-acid substitutions close to the N-terminal of TSC1 reduce steady-state levels of TSC1, resulting in the activation of mTOR signalling and leading to the symptoms of TSC.

A familial CHARGE syndrome with a CHD7 nonsense mutation and new clinical features.

The autosomal dominant CHARGE syndrome (MIM musical sharp214800) is caused by mutations in the CHD7 gene. It is usually sporadic but a few cases with gonadal mosaicism and familial inheritance have been reported. We describe a familial CHARGE syndrome in a two-generation Finnish family with a nonsense mutation in the CHD7 gene. Detailed clinical examination of the affected family members was performed, and mutations in the CHD7 gene were analysed with direct sequencing and multiplex ligation-dependent probe amplification. A nonsense mutation, p.Q1599X, was detected in exon 21 of the CHD7 gene in three affected family members. The father was only mildly affected, whereas his son had a very severe manifestation of the syndrome, causing death at the age of 3 months. The second pregnancy was prematurely terminated in the 23rd week because of cardiac anomalies detected in the ultrasound scan. The father's brother also had mild symptoms, but no mutation was detected in him. In this report, the variability of clinical symptoms within families and the clinical importance of mildly affected patients with the CHARGE syndrome are underlined with implications for molecular genetic diagnostics of the syndrome. Features not described in the CHARGE syndrome before are also presented.

Neuropathic symptoms and findings in women with Fabry disease.

OBJECTIVE: To examine the neurologic and neurophysiologic findings and neurologic symptoms in 12 women with Fabry disease and to study the relationship between the subjective symptoms and the findings on the various tests done. METHODS: Neurography, vibratory and thermal quantitative sensory testing (QST), skin biopsy for measuring intraepidermal nerve fiber density (IENFD). Heart rate variability (HRV) and sympathetic skin response (SSR) tests for detecting autonomic dysfunction, pain-, depression- and somatic symptom questionnaires and clinical examination. RESULTS: Only two women had no persistent symptoms or signs of polyneuropathy, 10 had symptoms of small fiber neuropathy. Neurological examination was normal in most patients. Five patients had decreased IENFD or thermal hypoesthesia in QST. In QST, Adelta-fiber function for innocuous cold was more often impaired than C-fiber function. Conventional nerve conduction studies were mostly normal. Carpal tunnel syndrome (CTS) incidence was increased, 25% had symptomatic CTS. CONCLUSIONS: Heterozygous women carrying the gene for Fabry disease have symptoms and findings of small-fiber polyneuropathy more often than has previously been considered. The prevalence of CTS is also increased. SIGNIFICANCE: While the clinical diagnosis of small-fiber neuropathy is difficult, the diagnostic yield can be increased using a combination of thermal QST and IENFD measurements.

Molecular analysis of the CHD7 gene in CHARGE syndrome: identification of 22 novel mutations and evidence for a low contribution of large CHD7 deletions.

PURPOSE: Autosomal dominant CHARGE syndrome (OMIM no. 214800) is characterized by choanal atresia or cleft lip or palate, ocular colobomas, cardiovascular malformations, retardation of growth, ear anomalies, and deafness, and is caused by mutations in the CHD7 gene. Here, we describe the outcome of a molecular genetic analysis in 18 Finnish and 56 German patients referred for molecular confirmation of the clinical diagnosis of suspected CHARGE syndrome. METHODS: Quantitative real-time polymerase chain reaction or multiplex ligation-dependent probe amplification assays did not reveal deletions in mutation negative cases, suggesting that larger CHD7 deletions are not a major cause of CHARGE syndrome. RESULTS: In this group of 74 patients, we found mutations in 30 cases. 22 mutations were novel, including 11 frameshift, 5 nonsense, 3 splice-site, and 3 missense mutations. One de novo frameshift mutation was found in the last exon and is expected to result in a minimally shortened CHD7 polypeptide. Because the mutation is associated with a typical CHARGE syndrome phenotype, it may indicate the presence of an as yet unknown functional domain in the very carboxyterminal end of CHD7. CONCLUSIONS: Our mutation detection rate of 40.5% is reflective of screening an unselected sample population referred for CHD7 testing based on suspected clinical diagnosis of CHARGE syndrome and not for having met strict clinical criteria for this disorder.

Townes-Brocks syndrome: twenty novel SALL1 mutations in sporadic and familial cases and refinement of the SALL1 hot spot region.

Townes-Brocks syndrome (TBS) is an autosomal dominant malformation syndrome characterized by renal, anal, ear, and thumb anomalies caused by SALL1 mutations. To date, 36 SALL1 mutations have been described in TBS patients. All but three of those, namely p.R276X, p.S372X, and c.1404dupG, have been found only in single families thereby preventing phenotype-genotype correlations. Here we present 20 novel mutations (12 short deletions, five short duplications, three nonsense mutations) in 20 unrelated families. We delineate the phenotypes and report previously unknown ocular manifestations, i.e. congenital cataracts with unilateral microphthalmia. We show that 46 out of the now 56 SALL1 mutations are located between the coding regions for the glutamine-rich domain mediating SALL protein interactions and 65 bp 3' of the coding region for the first double zinc finger domain, narrowing the SALL1 mutational hotspot region to a stretch of 802 bp within exon 2. Of note, only two SALL1 mutations would result in truncated proteins without the glutamine-rich domain, one of which is reported here. The latter is associated with anal, ear, hand, and renal manifestations, indicating that the glutamine-rich domain is not required for typical TBS.

Structural and functional changes in peripheral vasculature of Fabry patients.

OBJECTIVE: Fabry disease is a lysosomal storage disorder due to deficient alpha-galactosidase A activity, which leads to glycosphingolipid accumulation especially in vascular smooth-muscle and endothelial cells. Little is known about the effects of Fabry disease on peripheral artery function and structure. Therefore, we aimed to further characterize the peripheral vascular structural and functional changes in Fabry disease. METHODS AND RESULTS: We measured structural and functional vascular parameters, including intima-media thickness (IMT) of brachial and carotid arteries and abdominal aorta, carotid and aortic compliance, and brachial artery flow-mediated dilatation (FMD) in 17 Fabry patients and 34 healthy controls matched for age, sex and smoking. Carotid IMT (0.64 +/- 0.15 vs 0.57 +/- 0.12 mm), brachial IMT (1.02 +/- 0.25 vs 0.74 +/- 0.18 mm), and aortic IMT (0.31 +/- 0.09 vs 0.26 +/- 0.04 mm) were significantly increased, and brachial FMD was significantly impaired (6.3 +/- 5.0 vs 9.7 +/- 3.9%) in Fabry patients compared to healthy controls (p < 0.05 in all comparisons after adjustments for age, LDL-cholesterol, and systolic blood pressure). No differences were observed in arterial compliance between the groups. CONCLUSIONS: These data suggest that Fabry disease affects arterial function and structure by disturbing peripheral endothelial function and promoting intima-media thickening.

Delineation of the ADULT syndrome phenotype due to arginine 298 mutations of the p63 gene.

The ADULT syndrome (Acro-Dermato-Ungual-Lacrimal-Tooth, OMIM 103285) is a rare ectodermal dysplasia associated with limb malformations and caused by heterozygous mutations in p63. ADULT syndrome has clinical overlap with other p63 mutation syndromes, such as EEC (OMIM 604292), LMS (OMIM 603543), AEC (106260), RHS (129400) and SHFM4 (605289). ADULT syndrome characteristics are ectrodactyly, ectodermal dysplasia, mammary gland hypoplasia and normal lip and palate. The latter findings allow differentiation from EEC syndrome. LMS differs by milder ectodermal involvement. Here, we report three new unrelated ADULT syndrome families, all with mutations of arginine 298. On basis of 16 patients in five families with R298 mutation, we delineate the ADULT syndrome phenotype. In addition, we have documented a gain-of-function effect on the dNp63gamma isoform caused by this mutation. We discuss the possible relevance of oral squamous cell carcinoma in one patient, who carries this p63 germline mutation.

Detection of the founder effect in Finnish CADASIL families.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited cerebrovascular disease characterized by brain infarcts, cognitive decline and dementia. The disease is caused by at least 91 missense mutations, four deletions and one splice site mutation in the NOTCH3 gene, which maps to 19p13.1. In 18 out of the 21 Finnish CADASIL families so far identified, the causative mutation is an arginine to cysteine substitution in position 133 (R133C). Most of the families carrying this mutation originate from the western coast of Finland, thus suggesting a founder effect. No previous reports of a founder effect in CADASIL have been published. We haplotyped 60 patients from these 18 families for 10 microsatellite markers in order to determine whether the families descend from a common ancestor. We found a similar haplotype linked to the mutation in all 18 pedigrees, which indicates a single common ancestor for all the Finnish R133C families. The age analysis of the founder mutation places the introduction of the mutation in the late 1600s or early 1700s.

Dissecting the epidemiology of a trinucleotide repeat disease - example of FRDA in Finland.

Friedreich ataxia (FRDA) is associated with the expansion of a GAA trinucleotide repeat in the first intron of the frataxin (X25) gene. Worldwide it is considered to be the most common form of hereditary ataxia, but it is infrequently encountered in Finland. We have performed the first epidemiological study on the frequency of FRDA in Finland by combining results from a nationwide clinical survey and a molecular carrier testing study. Haplotype analysis was performed for the Finnish FRDA patients and the distribution of frataxin gene GAA repeats was analyzed in controls. In the general population of Finland, the carrier frequency was only 1 in 500, corresponding to a birth incidence of 1 in 10(6). In the more sparsely populated Northern Finland the carrier frequency was five times higher and also four out of the seven Finnish FRDA patients originated from this region. Haplotype analysis revealed the major universal risk haplotype in all the investigated patients. Alleles in the uppermost end of the normal variation (28-36 GAA) were totally missing in the Finnish population. The relative enrichment of the FRDA mutation in the north probably dates back to the internal migration movement and inhabitation of northern Finland in the 1500s. Breaking down the epidemiology of FRDA into clinical and molecular components brings along the possibility of providing more reliable and population-based genetic counseling and recurrence risk estimations.