Point mutation tRNA(Ser(UCN)) in a child with hearing loss and myoclonus epilepsy

We report on a family with a 12-year-old boy who suffered from a maternally inherited syndrome characterized by a combination of sensorineural hearing loss, myoclonus epilepsy, ataxia, severe psychomotor retardation, short stature, and diabetes mellitus. First, he showed a muscular hypotonia with hearing loss; later, he developed a myoclonus epilepsy, growth failure, and severe psychomotor retardation. At the age of 10 years, he developed diabetes mellitus. After initiation of combined ubiquinone and vitamin C treatment, we observed a progression in psychomotor development. Lactate and pyruvate levels in blood and cerebrospinal fluid were normal. No ragged red fibers or ultrastructural abnormalities were seen in a skeletal muscle biopsy. Biochemical assays of respiratory chain complex activities revealed decreased activity of complexes I and IV. By sequence analysis of mitochondrial DNA encoding transfer ribonucleic acids (RNAs), a homoplasmic T to C substitution at nucleotide position 7512 was found affecting a highly conserved base pair in the tRNA(ser(UCN)) acceptor stem. Asymptomatic family members of the maternal line were heteroplasmic for the mutation in blood samples. Analysis of mitochondrial DNA in patients with hearing loss and myoclonus epilepsy is recommended, even in the absence of laboratory findings. Therapeutically, ubiquinone and antioxidants can be beneficial.

Novel mutation in the ceruloplasmin gene causing a cognitive and movement disorder with diabetes mellitus

In a Chinese woman who had diabetes mellitus, undetectable ceruloplasmin, hand tremor, neck dystonia, and cognitive disturbances, genetic analyses revealed a novel homozygous mutation (848G > C or W283S) in exon 5 in the ceruloplasmin gene. Another member with a milder phenotype was also affected by this mutation. The healthy sister was heterozygous at the same position. Aceruloplasminemia has not yet been reported in China. This case suggests that increased awareness should be paid to this disorder in the presence of the typical symptoms.

A common origin of the 4143insA ADAMTS13 mutation

Severely deficient activity of the von Willebrand Factor (VWF) cleaving metalloprotease, ADAMTS13, is associated with thrombotic thrombocytopenic purpura (TTP). The mutation spectrum ofADAMTS13 is rather heterogeneous, and numerous mutations spread across the gene have been described in association with congenital TTP. The 4143insA mutation is unusual with respect to its geographic concentration. Following the initial report from Germany in which the 4143insA mutation was detected in four apparently unrelated families, we have now identified this mutation in a further eleven patients from Norway, Sweden, Poland, Germany, the Czech Republic and Australia. Confirmation that the Australian patient is of German ancestry, together with the Northern and Central European origin of most of the other patients, suggests that the 4143insA mutation has a common genetic background. We established ADAMTS13 haplotypes by analyzing 17 polymorphic intragenic markers. The haplotypes linked to 4143insA were identical in all informative families. Three novel candidate mutations, C347S, P671L and R1060W, as well as the known mutation R507Q, were also identified during the course of the study. We conclude that 4143insA has a common genetic background and is frequent among patients with hereditary ADAMTS13 deficiency in Northern and Central European countries.

A noncoding melanophilin gene (MLPH) SNP at the splice donor of exon 1 represents a candidate causal mutation for coat color dilution in dogs

Coat color dilution in several breeds of dog is characterized by a specific pigmentation phenotype and sometimes accompanied by hair loss and recurrent skin inflammation, the so-called color dilution alopecia or black hair follicular dysplasia. Coat color dilution (d) is inherited as a Mendelian autosomal recessive trait. In a previous study, MLPH polymorphisms showed perfect cosegregation with the dilute phenotype within breeds. However, different dilute haplotypes were found in different breeds, and no single polymorphism was identified in the coding sequence that was likely to be causative for the dilute phenotype. We resequenced the 5'-region of the canine MLPH gene and identified a strong candidate single nucleotide polymorphism within the nontranslated exon 1, which showed perfect association to the dilute phenotype in 65 dilute dogs from 7 different breeds. The A/G polymorphism is located at the last nucleotide of exon 1 and the mutant A-allele is predicted to reduce splicing efficiency 8-fold. An MLPH mRNA expression study using quantitative reverse transcriptase-polymerase chain reaction confirmed that dd animals had only about approximately 25% of the MLPH transcript compared with DD animals. These results provide preliminary evidence that the reported regulatory MLPH mutation might represent a causal mutation for coat color dilution in dogs.

A common ancestral glycoprotein (GP) 9 1828A>G (Asn45Ser) gene mutation occurring in European families from Australia and Northern Europe with Bernard-Soulier Syndrome (BSS)

Bernard-Soulier syndrome (BSS) is an extremely rare hereditary bleeding disorder, caused by mutations occurring in the Glycoprotein (GP) Ibalpha, GPIbbeta and GP9 genes that encode for the corresponding subunits of platelet GPIb-V-IX adhesion receptor complex. BSS has been reported in many populations, mostly behaving in an autosomal-recessive manner.While the great majority of BSS mutations are unique to a single individual or family, the GP9 1828A>G Asn45Ser mutation, which we have identified in an undocumented Australian Caucasian, has already been reported in multiple unrelated Caucasian families from various Northern and Central European countries. Haplotype analysis of 19 BSS patients from 15 unrelated Northern European families (including 2 compound heterozygote siblings from a British family previously published, and 17 1828A>G Asn45Ser homozygotes), showed that 14 of these BSS patients from 11 of the 1828A>G Asn45Ser homozygote families share a common haplotype at the chromosomal region 3' to the GP9 gene. Hence, the results suggest that the GP9 1828A>GAsn45Ser mutation in these families is ancient, and its frequent emergence in the European population is the result of a founder effect rather than recurrent mutational events. Association of the 1828A>G Asn45Ser mutation with variant haplotypes in 4 other Northern European BSS families raised the possibility of a second founder event, or rare recombinations in these families. Additional members from these 'atypical' lineages would need to be screened to resolve this question.

Unilateral focal polymicrogyria in a patient with classical Aarskog-Scott syndrome due to a novel missense mutation in an evolutionary conserved RhoGEF domain of the faciogenital dysplasia gene FGD1

Faciogenital dysplasia or Aarskog-Scott syndrome (AAS) is an X-linked disorder characterized by craniofacial, skeletal, and urogenital malformations and short stature. Mutations in the only known causative gene FGD1 are found in about one-fifth of the cases with the clinical diagnosis of AAS. FGD1 is a guanine nucleotide exchange factor (GEF) that specifically activates the Rho GTPase Cdc42 via its RhoGEF domain. The Cdc42 pathway is involved in skeletal formation and multiple aspects of neuronal development. We describe a boy with typical AAS and, in addition, unilateral focal polymicrogyria (PMG), a feature hitherto unreported in AAS. Sequencing of the FGD1 gene in the index case and his mother revealed the presence of a novel mutation (1396A>G; M466V), located in the evolutionary conserved alpha-helix 4 of the RhoGEF domain. M466V was not found in healthy family members, in >300 healthy controls and AAS patients, and has not been reported in the literature or mutation databases to date, indicating that this novel missense mutation causes AAS, and possibly PMG. Brain cortex malformations such as PMG could be initiated by mutations in the evolutionary conserved RhoGEF domain of FGD1, by perturbing the signaling via Rho GTPases such as Cdc42 known to cause brain malformation.

Exon splice enhancer mutation (GH-E32A) causes autosomal dominant growth hormone deficiency

CONTEXT AND OBJECTIVE: Alteration of exon splice enhancers (ESE) may cause autosomal dominant GH deficiency (IGHD II). Disruption analysis of a (GAA) (n) ESE motif within exon 3 by introducing single-base mutations has shown that single nucleotide mutations within ESE1 affect pre-mRNA splicing. DESIGN, SETTING, AND PATIENTS: Confirming the laboratory-derived data, a heterozygous splice enhancer mutation in exon 3 (exon 3 + 2 A-->C) coding for GH-E32A mutation of the GH-1 gene was found in two independent pedigrees, causing familial IGHD II. Because different ESE mutations have a variable impact on splicing of exon 3 of GH and therefore on the expression of the 17.5-kDa GH mutant form, the GH-E32A was studied at the cellular level. INTERVENTIONS AND RESULTS: The splicing of GH-E32A, assessed at the protein level, produced significantly increased amounts of 17.5-kDa GH isoform (55% of total GH protein) when compared with the wt-GH. AtT-20 cells coexpressing both wt-GH and GH-E32A presented a significant reduction in cell proliferation as well as GH production after forskolin stimulation when compared with the cells expressing wt-GH. These results were complemented with confocal microscopy analysis, which revealed a significant reduction of the GH-E32A-derived isoform colocalized with secretory granules, compared with wt-GH. CONCLUSION: GH-E32A mutation found within ESE1 weakens recognition of exon 3 directly, and therefore, an increased production of the exon 3-skipped 17.5-kDa GH isoform in relation to the 22-kDa, wt-GH isoform was found. The GH-E32A mutant altered stimulated GH production as well as cell proliferation, causing IGHD II.

Novel mutation in OTC gene causes neonatal death in twin brothers

Ornithine transcarbamylase (OTC) deficiency is the most common inborn error of the urea cycle. OTC locus is located in the short arm of X-chromosome. Authors report a case of a woman who gave birth to monozygotic male twins who later died because of severe neonatal-onset hyperammonaemic encephalopathy caused by a novel mutation of OTC gene. Post-mortem liver biopsy was taken from the second twin; afterwards, blood was drawn from the mother for examination. DNA sequence data showed that the mother was a carrier of the same novel mutation that was previously detected in the case of her son. In OTC deficiency, detection of female carriers is important for genetic counselling and eventual prenatal diagnosis.

Mutation analysis of NPHP6/CEP290 in patients with Joubert syndrome and Senior-Løken syndrome

BACKGROUND: Nephronophthisis (NPHP) is an autosomal recessive cystic kidney disease that constitutes the most common genetic cause of renal failure in the first three decades of life. Using positional cloning, six genes (NPHP1-6) have been identified as mutated in NPHP. In Joubert syndrome (JBTS), NPHP may be associated with cerebellar vermis aplasia/hypoplasia, retinal degeneration and mental retardation. In Senior-Løken syndrome (SLSN), NPHP is associated with retinal degeneration. Recently, mutations in NPHP6/CEP290 were identified as a new cause of JBTS. METHODS: Mutational analysis was performed on a worldwide cohort of 75 families with SLSN, 99 families with JBTS and 21 families with isolated nephronophthisis. RESULTS: Six novel and six known truncating mutations, one known missense mutation and one novel 3 bp pair in-frame deletion were identified in a total of seven families with JBTS, two families with SLSN and one family with isolated NPHP.

Calcineurin inhibition or mutation enhances cell wall inhibitors against Aspergillus fumigatus

Calcineurin mutation or inhibition enhanced the antifungal morphological effect of cell wall inhibitors caspofungin or nikkomycin Z against Aspergillus fumigatus. Quantification of 1,3-beta-d-glucan revealed decreased amounts in the calcineurin A (DeltacnaA) mutant. Calcineurin can be an excellent adjunct therapeutic target in combination with other cell wall inhibitors against A. fumigatus.

Novel TULP1 mutation causing leber congenital amaurosis or early onset retinal degeneration

PURPOSE: To report a large, consanguineous Algerian family affected with Leber congenital amaurosis (LCA) or early-onset retinal degeneration (EORD). METHODS: All accessible family members underwent a complete ophthalmic examination, and blood was obtained for DNA extraction. Homozygosity mapping was performed with markers flanking 12 loci associated with LCA. The 15 exons of TULP1 were sequenced. RESULTS: Seven of 30 examined family members were affected, including five with EORD and two with LCA. All patients had nystagmus, hemeralopia, mild myopia, and low visual acuity without photophobia. Fundus features were variable among EORD patients: typical spicular retinitis pigmentosa or clumped pigmented retinopathy with age-dependent macular involvement. A salt-and-pepper retinopathy with midperipheral retinal pigment epithelium (RPE) atrophy was present in the older patients with LCA, whereas the retina appeared virtually normal in the younger ones. Both scotopic and photopic electroretinograms were nondetectable. Fundus imaging revealed a perifoveal ring of increased fundus autofluorescence (FAF) in the proband, and optical coherence tomography disclosed a thinned retina, mainly due to photoreceptor loss. Linkage analysis identified a region of homozygosity on chromosome 6, region p21.3, and mutation screening revealed a novel 6-base in-frame duplication, in the TULP1 gene. CONCLUSIONS: Mutation in the TULP1 gene is a rare cause of LCA/EORD, with only 14 mutations reported so far. The observed intrafamilial phenotypic variability could be attributed to disease progression or possibly modifier alleles. This study provides the first description of FAF and quantitative reflectivity profiles in TULP1-related retinopathy.