Gema Gordo

A New Overgrowth Syndrome is Due to Mutations in RNF125.

Overgrowth syndromes (OGS) are a group of disorders in which all parameters of growth and physical development are above the mean for age and sex. We evaluated a series of 270 families from the Spanish Overgrowth Syndrome Registry with no known OGS. We identified one de novo deletion and three missense mutations in RNF125 in six patients from four families with overgrowth, macrocephaly, intellectual disability, mild hydrocephaly, hypoglycemia, and inflammatory diseases resembling Sjögren syndrome. RNF125 encodes an E3 ubiquitin ligase and is a novel gene of OGS. Our studies of the RNF125 pathway point to upregulation of RIG‐I‐IPS1‐MDA5 and/or disruption of the PI3K‐AKT and interferon signaling pathways as the putative final effectors.

Clinical and molecular analyses of Beckwith-Wiedemann syndrome: Comparison between spontaneous conception and assisted reproduction techniques.

Beckwith–Wiedemann syndrome (BWS) is an overgrowth syndrome characterized by an excessive prenatal and postnatal growth, macrosomia, macroglossia, and hemihyperplasia. The molecular basis of this syndrome is complex and heterogeneous, involving genes located at 11p15.5. BWS is correlated with assisted reproductive techniques. BWS in individuals born following assisted reproductive techniques has been found to occur four to nine times higher compared to children with to BWS born after spontaneous conception. Here, we report a series of 187 patients with to BWS born either after assisted reproductive techniques or conceived naturally. Eighty‐eight percent of BWS patients born via assisted reproductive techniques had hypomethylation of KCNQ1OT1:TSS‐DMR in comparison with 49% for patients with BWS conceived naturally. None of the patients with BWS born via assisted reproductive techniques had hypermethylation of H19/IGF2:IG‐DMR, neither CDKN1 C mutations nor patUPD11. We did not find differences in the frequency of multi‐locus imprinting disturbances between groups. Patients with BWS born via assisted reproductive techniques had an increased frequency of advanced bone age, congenital heart disease, and decreased frequency of earlobe anomalies but these differences may be explained by the different molecular background compared to those with BWS and spontaneous fertilization. We conclude there is a correlation of the molecular etiology of BWS with the type of conception.

Molecular Analysis of BMPR2 , TBX4 , and KCNK3 and Genotype-Phenotype Correlations in Spanish Patients and Families With Idiopathic and Hereditary Pulmonary Arterial Hypertension

INTRODUCTION AND OBJECTIVES Recent advances in genetics have led to the discovery of new genes associated with pulmonary arterial hypertension, such as TBX4 and KCNK3. The phenotype and prognosis associated with these new genes have been scarcely described and their role in the Spanish population is unknown. The aim of this study was to characterize the genetics of a Spanish cohort of patients with idiopathic and hereditary pulmonary arterial hypertension and to describe the phenotype and prognostic factors associated with BMPR2 and the new genes (KCNK3 and TBX4). METHODS A total of 165 adult patients were screened for BMPR2, KCNK3, and TBX4 mutations, 143 with idiopathic pulmonary arterial hypertension and 22 with hereditary pulmonary arterial hypertension. Baseline characteristics and survival were compared among the different subgroups and predictors of poor outcomes were analyzed. We also performed family screening. RESULTS The genetic study identified a possibly associated mutation in 11.10% of the idiopathic cases (n = 16) and in 68.18% of the hereditary cases (n = 15). There were 19 mutations in BMPR2, 4 in TBX4, and 3 in KCNK3. The forms associated with TBX4 showed the highest survival rate (P < .01). Advanced functional class at diagnosis was the only factor associated with poor outcomes in the hereditary forms. In the family screening, 37.5% of relatives tested positive. CONCLUSIONS The genetics of pulmonary arterial hypertension in the Spanish population may differ from other populations, with a lower proportion of BMPR2 causative mutations. In our cohort, TBX4-related forms of pulmonary arterial hypertension showed a more benign course and late diagnosis was the only predictor of adverse outcomes in the hereditary forms of the disease.

Pitfalls of trio-based exome sequencing: imprinted genes and parental mosaicism— MAGEL2 as an example

Pitfalls of trio-based exome sequencing: imprinted genes and parental mosaicism— MAGEL2 as an example

Hypoinsulinaemic, hypoketotic hypoglycaemia due to mosaic genetic activation of PI3-kinase

Objective Genetic activation of the insulin signal-transducing kinase AKT2 causes syndromic hypoketotic hypoglycaemia without elevated insulin. Mosaic activating mutations in class 1A phospatidylinositol-3-kinase (PI3K), upstream from AKT2 in insulin signalling, are known to cause segmental overgrowth, but the metabolic consequences have not been systematically reported. We assess the metabolic phenotype of 22 patients with mosaic activating mutations affecting PI3K, thereby providing new insight into the metabolic function of this complex node in insulin signal transduction. Methods Three patients with megalencephaly, diffuse asymmetric overgrowth, hypoketotic, hypoinsulinaemic hypoglycaemia and no AKT2 mutation underwent further genetic, clinical and metabolic investigation. Signalling in dermal fibroblasts from one patient and efficacy of the mTOR inhibitor Sirolimus on pathway activation were examined. Finally, the metabolic profile of a cohort of 19 further patients with mosaic activating mutations in PI3K was assessed. Results In the first three patients, mosaic mutations in PIK3CA (p.Gly118Asp or p.Glu726Lys) or PIK3R2 (p.Gly373Arg) were found. In different tissue samples available from one patient, the PIK3CA p.Glu726Lys mutation was present at burdens from 24% to 42%, with the highest level in the liver. Dermal fibroblasts showed increased basal AKT phosphorylation which was potently suppressed by Sirolimus. Nineteen further patients with mosaic mutations in PIK3CA had neither clinical nor biochemical evidence of hypoglycaemia. Conclusions Mosaic mutations activating class 1A PI3K cause severe non-ketotic hypoglycaemia in a subset of patients, with the metabolic phenotype presumably related to the extent of mosaicism within the liver. mTOR or PI3K inhibitors offer the prospect for future therapy.

Clinical Implementation of Pharmacogenetic Testing in a Hospital of the Spanish National Health System: Strategy and Experience Over 3 Years

In 2014, we established a pharmacogenetics unit with the intention of facilitating the integration of pharmacogenetic testing into clinical practice. This unit was centered around two main ideas: i) individualization of clinical recommendations, and ii) preemptive genotyping in risk populations. Our unit is based on the design and validation of a single nucleotide polymorphism (SNP) microarray, which has allowed testing of 180 SNPs associated with drug response (PharmArray), and clinical consultation regarding the results. Herein, we report our experience in integrating pharmacogenetic testing into our hospital and we present the results of the 2,539 pharmacogenetic consultation requests received over the past 3 years in our unit. The results demonstrate the feasibility of implementing pharmacogenetic testing in clinical practice within a national health system.

CLAPO syndrome: identification of somatic activating PIK3CA mutations and delineation of the natural history and phenotype

PurposeCLAPO syndrome is a rare vascular disorder characterized by capillary malformation of the lower lip, lymphatic malformation predominant on the face and neck, asymmetry, and partial/generalized overgrowth. Here we tested the hypothesis that, although the genetic cause is not known, the tissue distribution of the clinical manifestations in CLAPO seems to follow a pattern of somatic mosaicism.MethodsWe clinically evaluated a cohort of 13 patients with CLAPO and screened 20 DNA blood/tissue samples from 9 patients using high-throughput, deep sequencing.ResultsWe identified five activating mutations in the PIK3CA gene in affected tissues from 6 of the 9 patients studied; one of the variants (NM_006218.2:c.248T>C; p.Phe83Ser) has not been previously described in developmental disorders.ConclusionWe describe for the first time the presence of somatic activating PIK3CA mutations in patients with CLAPO. We also report an update of the phenotype and natural history of the syndrome.

Molecular and clinical analysis of ALPL in a cohort of patients with suspicion of hypophosphatasia.

Hypophosphatasia (HPP) is a rare autosomal dominant or recessive metabolic disorder caused by mutations in the tissue nonspecific alkaline phosphatase gene (ALPL). To date, over 300 different mutations in ALPL have been identified. Disease severity is widely variable with severe forms usually manifesting during perinatal and/or infantile periods while mild forms are sometimes only diagnosed in adulthood or remain undiagnosed. Common clinical features of HPP are defects in bone and tooth mineralization along with the biochemical hallmark of decreased serum alkaline phosphatase activity. The incidence of severe HPP is approximately 1 in 300,000 in Europe and 1 in 100,000 in Canada. We present the clinical and molecular findings of 83 probands and 28 family members, referred for genetic analysis due to a clinical and biochemical suspicion of HPP. Patient referrals included those with isolated low alkaline phosphatase levels and without any additional clinical features, to those with a severe skeletal dysplasia. Thirty‐six (43.3%) probands were found to have pathogenic ALPL mutations. Eleven previously unreported mutations were identified, thus adding to the ever increasing list of ALPL mutations. Seven of these eleven were inherited in an autosomal dominant manner while the remaining four were observed in the homozygous state. Thus, this study includes a large number of well‐characterized patients with hypophosphatasemia which has permitted us to study the genotype:phenotype correlation. Accurate diagnosis of patients with a clinical suspicion of HPP is crucial as not only is the disease life‐threatening but the patients may be offered bone targeted enzymatic replacement therapy.

Familial hypercholesterolemia: a single-nucleotide variant (SNV) in mosaic at the Low density lipoprotein receptor (LDLR)

Introduction Familial hypercholesterolemia (FH) is most frequently caused by genetic variants in the LDLR gene. Most of LDLR pathogenic variants are missense, followed by splicing and deletion/insertions variants. Mosaicism is a genetic condition in which an individual shows more than one clone of cells with different genotypes. Objective Molecular characterization of a patient with hypercholesterolemia. Methods Genetic analysis of DNA from peripheral blood and saliva was performed by NGS, sanger sequencing and pyrosequencing technologies. Results NGS analysis detected the pathogenic variant LDLR:c.1951G>T:p.(Asp651Tyr) in 9%-12% of reads. The presence of the variant was confirmed by pyrosequencing analysis. Conclusion Herein, we report the first case of a mosaic single nucleotide variant affecting the LDLR gene in a patient with familial hypercholesterolemia. As has been described for other pathologies, mosaicism could be underestimated in FH and its detection will improve with the introduction of NGS technologies in the diagnostic routine.

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.