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Focuses on the R608del mutation in the acid sphingomyelinase gene (SMPDI) which is most prevalent among patients from Gran Canaria Island with Niemann-Pick disease type B. Causes of Niemann-Pick type A and B diseases; Description of the R608del mutation; Clinical, biochemical and genetical findings in people living in Canaria island.

The finding of a genotype-negative hypertrophic cardiomyopathy (HCM) pedigree with several affected members indicating a familial origin of the disease has driven this study to discover causative gene variants. Genetic testing of the proband and subsequent family screening revealed the presence of a rare variant in the MYBPC3 gene, c.3331-26T>G in intron 30, with evidence supporting cosegregation with the disease in the family. An analysis of potential splice-altering activity using several splicing algorithms consistently yielded low scores. Minigene expression analysis at the mRNA and protein levels revealed that c.3331-26T>G is a spliceogenic variant with major splice-altering activity leading to undetectable levels of properly spliced transcripts or the corresponding protein. Minigene and patient mRNA analyses indicated that this variant induces complete and partial retention of intron 30, which was expected to lead to haploinsufficiency in carrier patients. As most spliceogenic MYBPC3 variants, c.3331-26T>G appears to be non-recurrent, since it was identified in only two additional unrelated probands in our large HCM cohort. In fact, the frequency analysis of 46 known splice-altering MYBPC3 intronic nucleotide substitutions in our HCM cohort revealed 9 recurrent and 16 non-recurrent variants present in a few probands (≤ 4), while 21 were not detected. The identification of non-recurrent elusive MYBPC3 spliceogenic variants that escape detection by in silico algorithms represents a challenge for genetic diagnosis of HCM and contributes to solving a fraction of genotype-negative HCM cases., (© 2022. The Author(s).)

Missense and frameshift pathogenic variants and microdeletions involving TBL1XR1 gene have been described in patients with intellectual disability, autism, Rett-like features and schizophrenia, some of them with the clinical diagnosis of Pierpont syndrome, a rare pattern of multiple congenital anomalies, but others without dysmorphic findings or with non-specific ones, and also patients with only some of the features associated with Pierpont syndrome. We here present a case with a de novo novel missense variant in TBL1XR1 gene with overlapping features with Pierpont syndrome and autism, a neurobehavioral manifestation not previously reported in Pierpont syndrome. This patient expands the phenotypic spectrum of TBL1XR1 gene pathogenic variants., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Usher syndrome is a rare disorder causing retinitis pigmentosa, together with sensorineural hearing loss. Due to the phenotypic and genetic heterogeneity of this disease, the best method to screen the causative mutations is by high-throughput sequencing. In this study, we tested a semiconductor chip based sequencing approach with 77 unrelated patients, as a molecular diagnosis routine. In addition, Multiplex Ligation-dependent Probe Amplification and microarray-based Comparative Genomic Hybridization techniques were applied to detect large rearrangements, and minigene assays were performed to confirm the mRNA processing aberrations caused by splice-site mutations. The designed panel included all the USH causative genes (MYO7A, USH1C, CDH23, PCDH15, USH1G, CIB2, USH2A, ADGRV1, WHRN and CLRN1) as well as four uncertainly associated genes (HARS, PDZD7, CEP250 and C2orf71). The outcome showed an overall mutation detection ratio of 82.8% and allowed the identification of 42 novel putatively pathogenic mutations. Furthermore, we detected two novel nonsense mutations in CEP250 in a patient with a disease mimicking Usher syndrome that associates visual impairment due to cone-rod dystrophy and progressive hearing loss. Therefore, this approach proved reliable results for the molecular diagnosis of the disease and also allowed the consolidation of the CEP250 gene as disease causative for an Usher-like phenotype.

Partial duplications involving the long arm of the X chromosome are associated with mental retardation, short stature, microcephaly, hypopituitarism and a wide range of physical findings. We identified an inherited Xq26.2-Xq26.3 duplication in two brothers with severe mental retardation, hypotonia, growth delay, craniofacial disproportion and dental malocclusion. Chromosome analysis was normal and multiplex ligation-dependent probe amplification analysis detected duplication on Xq26. Further characterization by array comparative genomic hybridization and quantitative PCR helped to determine proximal and distal duplication breakpoints giving a size of approximately 2.8 Mb. The duplication encompasses 24 known genes, including the X-linked mental retardation genes ARHGEF6, PHF6, HPRT1 and SLC9A6. Clinical and molecular characterization of Xq duplications will shed more light into the phenotypic implication of functional disomy of X-chromosome genes.

Spinal muscular atrophy (SMA) is caused by mutations in the SMN1 gene. We have studied the molecular pathology of SMA in 745 unrelated Spanish patients using PCR-RFLP, SMN gene dosage analysis, linkage studies, long-range PCR and direct sequencing. Our systematic approach allowed us to complete genetic testing and risk assessment in 736 SMA patients (98.8%). Females were more frequently affected by the acute form of the disease (type I), whereas chronic forms (type II-III) predominated in males (p<0.008). Absence of the SMN1 gene was detected in 671 patients (90%), and hybrid SMN1-SMN2 genes were observed in 37 cases (5%). Furthermore, we detected 13 small mutations in 28 patients (3.8%), four of which were previously identified in other populations (c.91dupT; c.770&#95;780dup11; p.Tyr272Cys and p.Thr274Ile), while five mutations were found to date only in Spanish patients (c.399&#95;402delAGAG, p.Ile116Phe, p.Gln136Glu, c.740dupC and c.834+2T>G). The c.399&#95;402delAGAG mutation accounted for 1.9% of all Spanish SMA patients. Finally, we discovered four novel mutations: c.312dupA, c.411delT, p.Trp190X and p.Met263Thr. Our results confirm that most SMA cases are due to large genetic rearrangements in the repetitive region of the SMA locus, resulting in absence-dysfunction of the SMN1 gene. By contrast, ancestrally inherited small mutations are responsible for only a small number of cases. Four prevalent changes in exons 3 and 6 (c.399&#95;402delAGAG; c.770&#95;780dup11; p.Tyr272Cys; p.Thr274Ile) accounted for almost 70% of our patients with these subtle mutations. An SMN-SMN dimer model featuring tight hydrophobic-aromatic interactions is proposed to explain the impact of mutations at the C-terminal end of the protein.

Ataxia with isolated vitamin E deficiency is a rare autosomal recessive neurodegenerative disease due to mutations in the alpha-tocopherol transfer protein gene. In ataxia with isolated vitamin E deficiency, the biochemical hallmark is the low plasmatic levels of vitamin E and, in most of the patients, vitamin E supplementation allows a stabilization of the neurologic conditions. We have investigated the genetic cause of ataxia and reduced levels of vitamin E, and apolipoproteins A1 and B in a 16-y-old patient. Results revealed that our propositus is a compound heterozygote for the c.227&#95;229delinsATT/c.744delA mutations in the alpha-tocopherol transfer protein gene, each inherited from one of the two parents. His sister is also a compound heterozygote for both mutations, and she presents a biochemical pattern similar to that of his brother. After receiving the vitamin E supplementation, plasmatic levels of vitamin E and apolipoprotein A1 have been normalized in the propositus. The detected mutations would justify the undetectable levels of vitamin E, but would not explain the also decreased levels of the apolipoproteins, as neither that after treatment with vitamin E, the levels of apolipoprotein B do not become normal. These findings suggest that other genes may play a role in producing this atypical biochemical profile.

Purpose: Routine protocols for the study of mental retardation include karyotype, analysis for fragile X syndrome, and subtelomeric rearrangements. Nevertheless, detection of cryptic rearrangements requires more sensitive techniques. Mutation screening in all known genes responsible for X-linked mental retardation is not feasible, and linkage analysis is sometimes limited. Multiplex ligation probe amplification is a recently developed technique based on the amplification of specific probes that allows relative quantification of 40 to 46 different target DNA sequences in a single reaction., Methods: In the present study, we assessed multiplex ligation probe amplification for the detection of microduplications/microdeletions in 80 male patients with suspicion of X-linked mental retardation., Results: We detected four copy number aberrations (5%): three duplications (GDI1, RPS6KA3, and ARHGEF6) and one deletion (OPHN1). All these changes were confirmed by other molecular techniques, and patients were clinically re-evaluated., Conclusions: We strongly recommend the use of multiplex ligation probe amplification as a first screening method for the detection of copy number aberrations in patients with mental retardation because of its cost-effectiveness.

Adult dominant polycystic kidney disease is an hereditary condition responsible for 6% of end-stage renal failure in Spain. Two genes were located in chromosomes 16 and 4 as related to this age-dependent disease in the 90s (PKD1 and PKD2). The diagnosis can be easily achieved by sonographic study, but molecular analysis by means of linkage analysis has the advantage of an early diagnosis in asymptomatic genetic carriers, with a view to the preventive follow-up of these subjects and genetic counselling. In this paper we present the results of molecular analysis of 30 families with Adult Dominant Polycystic Kidney Disease (from the province of Las Palmas Spain), carried out linkage analysis with two series of microsatellite markers located within or in the vicinity ofPKD1 (D16S521, KG8, AC2.5, CW2, SM7) and PKD2 (D4S1538, D4S1534, D4S423,D4S414) genes. The objectives of the study were: first, to verify the informativeness, and therefore, the usefulness of these markers for family studies in our population; and second,to assess the sensitivity and specificity of the genetic analysis in our population. Most of the markers showed a high heterozygosity, comparable to data in other studies. Considering the alleles of the different markers together in a chromosome as an haplotype increased the informativeness of the markers, and allowed the unequivocal identification of genetic data in 97.7% of patients and 88.7% of healthy subjects. The sensitivity and specificity of the genetic analysis were 90.7% (CI 95%: 85.7-95.7) and 86.8% (CI 95%: 80.6-93.0), respectively.

Mutations in the Connexin-26 gene are responsible for up to 60% of nonsyndromic, neurosensory autosomal recessive deafness (NSRD). Amongst all the mutations described to date, 35delG (a deletion of a G in a tract of five Gs at positions 30-35) is the most common and has been found in virtually all of the populations studied. Because its frequency varies in different populations, a rapid and simple method of detection of this mutation would be very helpful in population studies. A wide variety of methods for this detection have been described, but we herein present a very simple method using a PCR with primers designed to provide an amplicon of 94 or 93 nucleotides for the normal or mutant alleles, respectively, that can be easily distinguished in an 8% polyacrylamide gel. The entire protocol can be completed in a morning, thus supporting multiple runs. This assay will be useful in screening the large sample sizes required for population studies.

Case Reports: We report the cases of four males from four different families, who presented paroxysmal episodes from the 1st 2nd year. These episodes were characterised by asymmetrical bilateral dystonia of the upper limbs, predominantly in both hands, and were associated with orofacial dyskinesias, stereotipies (jumping, arm flapping, etc.), facial tics and, occasionally, phonic tics. Consciousness is not affected in any of the cases. These movements are triggered in situations where the patient is relaxed or excited. They occur daily and last from a few seconds to 30 minutes. Between the bouts, they remain asymptomatic. Family cases suggest it is inherited by autosomal dominant transmission, perhaps linked to the X chromosome; in addition, two cases are sporadic. In the only adult, the movements progress to a series of rhythmic bilateral dystonic myoclonias and facial tics dyskinesias. All the studies carried out, EEG, hemogram, biochemical analysis, neuroimaging, copper and ceruloplasmin levels, were normal., Conclusions: 1. We report a non epileptic paroxysmal disorder originating in the extrapyramidal tracts with its own characteristics, with onset during early childhood, which is associated with stereotipies, tics and dystonia; 2. It occurs predominantly in males; 3. It is inherited by autosomal dominant transmission, or perhaps sex linked autosomal dominant inheritance, and there are also sporadic cases; 4. The range of clinical features is very wide and includes cases in which there are few symptoms to others where the extent and gravity of the disorder is very significant.

Introduction and Clinical Cases: The Pitt Rogers Danks syndrome is characterized by prenatal and postnatal retardation of growth, mental retardation, microcephaly, convulsions and a peculiar facies. It is believed to represent a clinical variant of the Wolf Hirschhorn syndrome, since there is a deletion in the 4p16.3 region in both syndromes. We report two cases in the same family caused by maternal mal segregation of a 4:8 balanced translocation. We describe the clinical characteristics, investigations done and a review of the literature.

Molecular screening programs in mentally retarded individuals have been performed in several populations worldwide. One finding has been an excess of FMR1 intermediate alleles in a population with learning difficulties. However, other published reports with similar characteristics did not corroborate those previous results. In order to contribute additional data from our population, we studied 563 patients affected with nonspecific mental retardation (MRX) that did not present a CGG expansion in the FMR1 gene and 208 individuals as a control population. Forty MRX patients presented alleles within the intermediate range. Among them, one case showed a pattern of expression of the FMR1 protein (FMRP) concordant with a fragile X syndrome case with an intermediate allele/full mutation mosaicism, although it was not detected by Southern blot analysis. Statistical analysis was performed again showing no statistically significant difference regarding the intermediate allele frequency in the MRX and control populations. This finding is in agreement with the hypothesis that the incidence of intermediate FMR1 alleles in MRX populations does not seem to be higher than in control populations, and it emphasizes the importance of FMRP detection as a diagnostic tool for fragile X syndrome.