mTOR mutations in Smith-Kingsmore syndrome: Four additional patients and a review.

Smith-Kingsmore syndrome (SKS) OMIM #616638, also known as MINDS syndrome (ORPHA 457485), is a rare autosomal dominant disorder reported so far in 23 patients. SKS is characterized by intellectual disability, macrocephaly/hemi/megalencephaly, and seizures. It is also associated with a pattern of facial dysmorphology and other non-neurological features. Germline or mosaic mutations of the mTOR gene have been detected in all patients. The mTOR gene is a key regulator of cell growth, cell proliferation, protein synthesis and synaptic plasticity, and the mTOR pathway (PI3K-AKT-mTOR) is highly regulated and critical for cell survival and apoptosis. Mutations in different genes in this pathway result in known rare diseases implicated in hemi/megalencephaly with epilepsy, as the tuberous sclerosis complex caused by mutations in TSC1 and TSC2, or the PIK3CA-related overgrowth spectrum (PROS). We here present 4 new cases of SKS, review all clinical and molecular aspects of this disorder, as well as some characteristics of the patients with only brain mTOR somatic mutations.

PLP1 gene analysis in 88 patients with leukodystrophy.

Pelizaeus-Merzbacher disease (PMD) is caused in most cases by either duplications or point mutations in the PLP1 gene. This disease, a dysmyelinating disorder affecting mainly the central nervous system, has a wide clinical spectrum and its causing mutations act through different molecular mechanisms. Eighty-eight male patients with leukodystrophy were studied. PLP1 gene analysis was performed by the Multiplex Ligation-dependent Probe Amplification technique and DNA sequencing, and, in duplicated cases of PLP1, gene dosage was completed by using array-CGH. We have identified 21 patients with mutations in the PLP1 gene, including duplications, short and large deletions and several point mutations in our cohort. A customized array-CGH at the Xq22.2 area identified several complex rearrangements within the PLP1 gene region. Mutations found in the PLP1 gene are the cause of PMD in around 20% of the patients in this series.

Foetal sex determination in maternal blood from the seventh week of gestation and its role in diagnosing haemophilia in the foetuses of female carriers.

The existence of foetal DNA in maternal blood, discovered in 1997, opened new possibilities for noninvasive prenatal diagnosis. This includes foetal sex assessment by the detection of specific Y chromosome sequences in maternal blood, particularly important when a foetus may be affected by an X-linked disorder such as haemophilia. This study aims to validate this sex assessment method and to test its clinical utility in the diagnosis of 15 potentially affected pregnancies in female carriers of haemophilia. In the validation study, 316 maternal blood samples from 196 pregnant women at gestations ranging from 5 weeks to 12 weeks were analysed. In the clinical study, 15 pregnancies at risk of having a haemophilic foetus were tested. All pregnancies in the validation study were correctly diagnosed. The accuracy and specificity of the methodology from the seventh week of gestation was 100%. The sex of all 15 pregnancies identified as being at risk of bearing a haemophilic foetus was correctly diagnosed. Foetal sex assessment by detecting specific Y chromosome sequences in maternal blood is now routinely used in our hospital because of its high accuracy from the seventh week of gestation. Reliable foetal gender determination from maternal blood of pregnant women carriers of haemophilia in the first trimester of gestation can avoid more conventional, invasive methods of prenatal diagnosis.

Next generation sequencing in the diagnosis of Stargardt's disease. / La secuenciación masiva (NGS) como método diagnóstico en la enfermedad de Stargardt.

INTRODUCTION: Stargardt's disease is the most frequent form of inherited macular dystrophy in children and adults. It is a genetic eye disorder caused by mutations in ABCA4 gene with an autosomal recessive inheritance. ABCA4 is a very polymorphic and large gene containing 50 exons. The development of next generation sequencing (NGS) can be used for the genetic diagnosis of this disease. PATIENTS AND METHODS: A report is presented on two patients with a clinical diagnosis of Stargardt's disease whose genetic confirmation was performed by a NGS panel of 298 genes. RESULTS: Clinically, the patients showed bull's eye maculopathy and absence of flecks, and genetically they shared the Gly1961Glu mutation that could explain their common phenotype, together with c.C3056T:p.T1019M for case 1, and c.287del:p.Asn96Thrfs*19 for case 2. CONCLUSIONS: NGS is particularly useful in the diagnosis of Stargardt's disease as ABCA4 is a large gene with a high allelic heterogeneity that causes a wide range of clinical manifestations.

Partial paternal uniparental disomy (UPD) of chromosome 1 in a patient with Stargardt disease.

PURPOSE: Stargardt disease (STGD) is the most common juvenile macular dystrophy, characterized by central visual impairment. All recessively inherited cases are thought to be due to mutations in the ABCA4 gene, mapped to 1p21-p13. METHODS: To describe a form of non-mendelian inheritance in a patient with STGD identified through the course of a conventional mutational screening performed on 77 STGD families. DNA from the patient and relatives was analyzed for variants in all 50 exons of the ABCA4 gene by screening on the ABCR400 microarray; results were confirmed by direct sequencing. Haplotype analyses, standard and high-resolution (HR) karyotypes, and multiplex ligation-dependent probe amplification (MLPA) were also performed. RESULTS: A patient with STGD caused by the homozygous p.Arg1129Leu mutation in the ABCA4 gene was found to be the daughter of a noncarrier mother and a father who was heterozygous for this change. Haplotype analysis suggested that no maternal ABCA4 allele was transmitted to the patient. Microsatellite markers spanning the entire chromosome 1 identified a homozygous region of at least 4.4 Mb, involving the ABCA4 gene. The cytogenetic study revealed normal female karyotype. Further evaluation with MLPA showed the patient had a normal dosage for both copies of the ABCA4 gene, thus suggesting partial paternal isodisomy but not a maternal microdeletion. CONCLUSIONS: We report that recessive STGD can rarely be inherited from only one unaffected carrier parent in a non-mendelian manner. This study also demonstrates that genomic alterations contribute to only a small fraction of disease-associated alleles for ABCA4.

Living donor renal transplantation in Catalonia: overall results and comparison of survival with cadaveric donor renal transplantation.

OBJECTIVES: To describe the general characteristics of living-donor renal transplantation (LRT) in Catalonia, and to compare results with those of the cadaveric donor renal transplant (CRT). RESULTS: Four hundred seventy-three LRTs have been performed in Catalonia since 1965. Transplantations carried out between 1980 and 2003, according to the RMRC data, were reviewed. The most frequent degrees of kinship are parents-children (48%), spouses (22%), and siblings (18%). Around 68% of the donors were women. Around 56% of recipients were men. The transplant was advanced in approximately 30% of the cases. The mean cold ischemia was 2 hours. Seven percent showed delayed graft function (DGF). Forty-nine percent of the patients had glomerular filtration >60 mL/min after 1 year. Patient survival at 1, 5, 10, and 20 years were 99%, 97%, 93%, and 82% in LRT; and 96%, 90%, 80%, and 62% in CRT (P < .00001). Graft survivals over the same periods were 91%, 76%, 58%, and 32% in LRT, and 85%, 69%, 49%, and 23% in CRT (P = .00008). The graft mean life was 12 years (LRT) and 10 years (CRT). Graft survivals, censoring deaths over the same periods, were 93%, 79%, 62%, and 39% in LRT, and 89%, 77%, 62%, and 37% in CRT (P = .3). Mean life was 14 years in both cases. The recipients mean age was 31 (LRT), and 44 years (CRT), whereas the donor mean age was 51 (LRT), and 42 years (CRT). CONCLUSIONS: LRT results were excellent both regarding DGF and patient and graft survivals. They were not comparable to CRT due to the different characteristics of the recipients. LRT is a good solution to reduce waiting lists.