Pedro Arias

Simpson-Golabi-Behmel syndrome types I and II

Simpson-Golabi-Behmel syndrome (SGBS) is a rare overgrowth syndrome clinically characterized by multiple congenital abnormalities, pre/postnatal overgrowth, distinctive craniofacial features, macrocephaly, and organomegaly. Abnormalities of the skeletal system, heart, central nervous system, kidney, and gastrointestinal tract may also be observed. Intellectual disability, early motor milestones and speech delay are sometimes present; however, there are a considerable number of individuals with normal intelligence.Genomic rearrangements and point mutations involving the glypican-3 gene (GPC3) at Xq26 have been shown to be associated with SGBS. Occasionally, these rearrangements also include the glypican-4 gene (GPC4). Glypicans are heparan sulfate proteoglycans which have a role in the control of cell growth and cell division.Although a lethal and infrequent form (also known as SGBS type II) has been described, only the classical form of SGBS is reviewed in this work, whereas only some specific features on SGBS type II are commented.We review all clinical and molecular aspects of this rare disorder, updating many topics and suggest a follow-up scheme for geneticists and primary care clinicians.ResumenEl Síndrome de Simpson-Golabi-Behmel (SSGB) es un Síndrome de sobrecrecimiento raro, que se caracteriza clínicamente por múltiples anomalías congénitas, sobrecrecimiento pre y post natal, rasgos craneofaciales distintivos, macrocefalia y organomegalia. Otras características que pueden presentar estos pacientes incluyen anomalías en el aparato esquelético, el corazón, el sistema nervioso central, el riñón y el tracto gastrointestinal. También pueden presentar discapacidad intelectual, retraso motor precoz y retraso en el habla, aunque en su mayoría, estos individuos presentan una inteligencia dentro de los límites normales.Los reordenamientos genómicos y las mutaciones puntuales que incluyen el gen GPC3 (“Glypican-3 gene”) localizado en la región cromosómica Xq26, se han asociado con la aparición del SSGB. Ocasionalmente, estos reordenamientos genómicos pueden incluir el gen GPC4. Los glipicanos son proteoglicanos de heparán sulfato que actúan controlando el crecimiento y división celular.Aunque se ha descrito una forma letal de este Síndrome (denominada SSGB tipo II) en esta revisión sólo analizamos la forma clásica de este Síndrome y sólo comentaremos algunos aspectos del SSGB tipo II.En este trabajo se presenta una revisión de todos los aspectos clínicos y moleculares de este Síndrome, actualizando algunos aspectos y además se sugiere un esquema de seguimiento de estos pacientes por parte de genetistas y médicos de atención primaria.

Germinal mosaicism in Simpson-Golabi-Behmel syndrome

To the Editor: Simpson-Golabi-Behmel syndrome (SGBS, OMIM 312870) is an X-linked overgrowth disorder comprising multiple congenital abnormalities and increased risk for the development of embryonal tumours (1, 2), mainly Wilms’ tumours, hepatoblastoma and neuroblastoma (1, 3–6). It is characterized by preand postnatal overgrowth, visceral and skeletal anomalies, coarse face, supernumerary nipples, congenital heart defects and hypotonia (7). The spectrum of clinical manifestations is broad, varying from very mild forms in carrier women to infantile lethal form in affected men (8). Mutations/ deletions of GPC3 localized at Xq26 have been observed in some SGBS patients (9, 10). Apparent lack of correlation between the extent of the deletions and the phenotypic expression of the disease was noted (11), leading to the conclusion that classical’ cases of SGBS are likely due to loss of function of GPC3 (12). We report on two brothers with SGBS. Patient 1 was born pre-maturely (34 weeks) 23 years ago after a pregnancy complicated by polyhydramnios. Birth weight was 2050 g (75–90th centile). Parents were young, healthy and non-consanguineous. He had a coarse face, ambiguous external genitalia, abdominaldistension,hypotonia, short fifthdigits and aheartmurmur [Fig. 1(a) and(b)].Hydronephrosis, duodenal atresia and heart defect (atrial septal defect and tricuspid valve hypoplasia) were also found. The patient’s clinical status worsened and finally died. Necropsy showed testes with adenomatous hyperplasia of the rete testis, Müllerian rests, bilateral hydronephrosis and nephroblastomatosis and adenomatous hyperplasia of rete testis. At the CNS, there was diffuse gliosis, isolated microcalcifications in the white matter and cerebellar cortical heterotopia. Karyotype was 46,XY. A diagnosis of multiple congenital anomalies/male pseudohermaphroditism of unknown cause and unknown recurrence risk was given to the family. Patient 2 is patient 1’s brother and was the couple’s fourth pregnancy. He had an older, healthy brother and his mother had had a spontaneous abortion in her third pregnancy. He was born by Cesarean section at 36 weeks after a pregnancy complicated by polyhydramnios and foetal macrosomia. Amniocentesis was 46,XY. Birth weight was 4500 g (.97th centile), length 54.5 cm (.97th centile) and OFC 36 cm (90th centile). He showed macrosomia, hypotonia, coarse face, macroglossia, macrostomia, short neck, single palmar crease, auricular tags, extra nipples, hypospadias, cryptorchidism, nephromegaly and anal atresia [Fig. 1 (c)–(f)]. After discharge, he was followed-up periodically by a paediatrician, who reported post-natal overgrowth, bilateral nephromegaly with cystic images in kidneys, liver and large, squared hands with short, stiff thumbs. His developmental milestones were normal, and he had no mental impairment. DNA samples from peripheral blood were obtained for patient 2 and his parents from paraffin-embedded tissues from patient 1. Deletions of the GPC3 and GPC4 genes were evaluated through multiplex ligation-dependent probe amplification (13) using the SALSA P154 kit (MRC-Holland, Amsterdam, The Netherlands). Sequence analysis using the primers reported by Huber et al. (14) were performed by duplicate in different DNA extractions and experiments in all individuals. Direct bi-directional sequencing of all GPC3 exons in patient 2 showed a C / T transition (c.1605 C.T) in exon 4, leading to a CGA / TGA change (R387X). This change was also found in ancient DNA of patient 1, but was not observed in their mother (Fig. 2). Such evidence led us to the conclusion that she probably had germinal mosaicism for this mutation. SGBS clinically resembles the Beckwith–Wiedemann syndrome (BWS) and Perlman syndrome (15). All three disorders display overgrowth, tumour predisposition and other occasional malformations. Patient 1 of this report showed coarse face, male pseudohermaphroditism with abnormal external genitalia and Müllerian rest, abdominal

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.

Identification of eight new mutations in the GCK gene by DHPLC screening in a Spanish population.

Maturity onset diabetes of the young (MODY) is a genetically heterogeneous disorder characterized by autosomal dominant inheritance, altered function of pancreatic beta cells and early onset diabetes mellitus, usually before 25 years old. The prevalence of specific mutations of MODY genes differs considerably among different countries. In this study we analyzed 53 index cases from unrelated MODY families who are potential carriers of mutations in GCK gene. In addition, 122 relatives were also studied. We have identified eight new mutations in the GCK gene. One of them is a non-frameshift deletion involving Lysine 143. This amino acid is part of the conserved stretch of basic residues (KHKKL) which spans from residue 140 to 144. The non-frameshift deletion might implicate the affinity of GCK for GCKRP, and potentially the abnormal nuclear localization of GCK. Additional studies should be performed to confirm this possibility.

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.

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.

Molecular characterization of breast cancer cell response to metabolic drugs

Metabolic reprogramming is a hallmark of cancer. It has been described that breast cancer subtypes present metabolism differences and this fact enables the possibility of using metabolic inhibitors as targeted drugs in specific scenarios. In this study, breast cancer cell lines were treated with metformin and rapamycin, showing a heterogeneous response to treatment and leading to cell cycle disruption. The genetic causes and molecular effects of this differential response were characterized by means of SNP genotyping and mass spectrometry-based proteomics. Protein expression was analyzed using probabilistic graphical models, showing that treatments elicit various responses in some biological processes such as transcription. Moreover, flux balance analysis using protein expression values showed that predicted growth rates were comparable with cell viability measurements and suggesting an increase in reactive oxygen species response enzymes due to metformin treatment. In addition, a method to assess flux differences in whole pathways was proposed. Our results show that these diverse approaches provide complementary information and allow us to suggest hypotheses about the response to drugs that target metabolism and their mechanisms of action.

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.