Jair Tenorio

Identification of a Mutation Causing Deficient BMP1/mTLD Proteolytic Activity in Autosomal Recessive Osteogenesis Imperfecta

Herein, we have studied a consanguineous Egyptian family with two children diagnosed with severe autosomal recessive osteogenesis imperfecta (AR‐OI) and a large umbilical hernia. Homozygosity mapping in this family showed lack of linkage to any of the previously known AR‐OI genes, but revealed a 10.27 MB homozygous region on chromosome 8p in the two affected sibs, which comprised the procollagen I C‐terminal propeptide (PICP) endopeptidase gene BMP1. Mutation analysis identified both patients with a Phe249Leu homozygous missense change within the BMP1 protease domain involving a residue, which is conserved in all members of the astacin group of metalloproteases. Type I procollagen analysis in supernatants from cultured fibroblasts demonstrated abnormal PICP processing in patient‐derived cells consistent with the mutation causing decreased BMP1 function. This was further confirmed by overexpressing wild type and mutant BMP1 longer isoform (mammalian Tolloid protein [mTLD]) in NIH3T3 fibroblasts and human primary fibroblasts. While overproduction of normal mTLD resulted in a large proportion of proα1(I) in the culture media being C‐terminally processed, proα1(I) cleavage was not enhanced by an excess of the mutant protein, proving that the Phe249Leu mutation leads to a BMP1/mTLD protein with deficient PICP proteolytic activity. We conclude that BMP1 is an additional gene mutated in AR‐OI. Hum Mutat 33:343–350, 2012.

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.

Prenatal molecular testing for Beckwith-Wiedemann and Silver-Russell syndromes: a challenge for molecular analysis and genetic counseling.

Beckwith–Wiedemann and Silver–Russell syndromes (BWS/SRS) are two imprinting disorders (IDs) associated with disturbances of the 11p15.5 chromosomal region. In BWS, epimutations and genomic alterations within 11p15.5 are observed in >70% of patients, whereas in SRS they are observed in about 60% of the cases. In addition, 10% of the SRS patients carry a maternal uniparental disomy of chromosome 7 11p15.5. There is an increasing demand for prenatal testing of these disorders owing to family history, indicative prenatal ultrasound findings or aberrations involving chromosomes 7 and 11. The complex molecular findings underlying these disorders are a challenge not only for laboratories offering these tests but also for geneticists counseling affected families. The scope of counseling must consider the range of detectable disturbances and their origin, the lack of precise quantitative knowledge concerning the inheritance and recurrence risks for the epigenetic abnormalities, which are hallmarks of these developmental disorders. In this paper, experts in the field of BWS and SRS, including members of the European network of congenital IDs (EUCID.net; www.imprinting-disorders.eu), put together their experience and work in the field of 11p15.5-associated IDs with a focus on prenatal testing. Altogether, prenatal tests of 160 fetuses (122 referred for BWS, 38 for SRS testing) from 5 centers were analyzed and reviewed. We summarize the current knowledge on BWS and SRS with respect to diagnostic testing, the consequences for prenatal genetic testing and counseling and our cumulative experience in dealing with these disorders.

Expert consensus document: Clinical and molecular diagnosis, screening and management of Beckwith-Wiedemann syndrome: an international consensus statement.

Beckwith–Wiedemann syndrome (BWS), a human genomic imprinting disorder, is characterized by phenotypic variability that might include overgrowth, macroglossia, abdominal wall defects, neonatal hypoglycaemia, lateralized overgrowth and predisposition to embryonal tumours. Delineation of the molecular defects within the imprinted 11p15.5 region can predict familial recurrence risks and the risk (and type) of embryonal tumour. Despite recent advances in knowledge, there is marked heterogeneity in clinical diagnostic criteria and care. As detailed in this Consensus Statement, an international consensus group agreed upon 72 recommendations for the clinical and molecular diagnosis and management of BWS, including comprehensive protocols for the molecular investigation, care and treatment of patients from the prenatal period to adulthood. The consensus recommendations apply to patients with Beckwith–Wiedemann spectrum (BWSp), covering classical BWS without a molecular diagnosis and BWS-related phenotypes with an 11p15.5 molecular anomaly. Although the consensus group recommends a tumour surveillance programme targeted by molecular subgroups, surveillance might differ according to the local health-care system (for example, in the United States), and the results of targeted and universal surveillance should be evaluated prospectively. International collaboration, including a prospective audit of the results of implementing these consensus recommendations, is required to expand the evidence base for the design of optimum care pathways.

Clinical, biochemical and genetic spectrum of low alkaline phosphatase levels in adults.

BACKGROUND Low serum levels of alkaline phosphatase (ALP) are a hallmark of hypophosphatasia. However, the clinical significance and the underlying genetics of low ALP in unselected populations are unclear. METHODS In order to clarify this issue, we performed a clinical, biochemical and genetic study of 42 individuals (age range 20-77yr) with unexplained low ALP levels. RESULTS Nine had mild hyperphosphatemia and three had mild hypercalcemia. ALP levels were inversely correlated with serum calcium (r=-0.38, p=0.012), pyridoxal phosphate (PLP; r=-0.51, p=0.001) and urine phosphoethanolamine (PEA; r=-0.49, p=0.001). Although many subjects experienced minor complaints, such as mild musculoskeletal pain, none had major health problems. Mutations in ALPL were found in 21 subjects (50%), including six novel mutations. All but one, were heterozygous mutations. Missense mutations were the most common (present in 18 subjects; 86%) and the majority were predicted to have a damaging effect on protein activity. The presence of a mutated allele was associated with tooth loss (48% versus 12%; p=0.04), slightly lower levels of serum ALP (p=0.002), higher levels of PLP (p<0.0001) and PEA (p<0.0001), as well as mildly increased serum phosphate (p=0.03). Ten individuals (24%) had PLP levels above the reference range; all carried a mutated allele. CONCLUSION One-half of adult individuals with unexplained low serum ALP carried an ALPL mutation. Although the associated clinical manifestations are usually mild, in approximately 50% of the cases, enzyme activity is low enough to cause substrate accumulation and may predispose to defects in calcified tissues.

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.

PIAS4 is associated with macro/microcephaly in the novel interstitial 19p13.3 microdeletion/microduplication syndrome

Array comparative genomic hybridization (aCGH) is a powerful genetic tool that has enabled the identification of novel imbalances in individuals with intellectual disability (ID), autistic disorders and congenital malformations. Here we report a ‘genotype first’ approach using aCGH on 13 unrelated patients with 19p13.3 submicroscopic rearrangement (11 deletions and 2 duplications) and review cases in the literature and in public databases. Shared phenotypic features suggest that these patients represent an interstitial microdeletion/microduplication syndrome at 19p13.3. Common features consist of abnormal head circumference in most patients (macrocephaly with the deletions and microcephaly with the duplications), ID with developmental delay (DD), hypotonia, speech delay and common dysmorphic features. The phenotype is associated with at least a ~0.113 Mb critical region harboring three strong candidate genes probably associated with DD, ID, speech delay and other dysmorphic features: MAP2K2, ZBTB7A and PIAS4, an E3 ubiquitin ligase involved in the ubiquitin signaling pathways, which we hypothesize for the first time to be associated with head size in humans.

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.

A novel mutation in CDKN1C in sibs with Beckwith–Wiedemann syndrome and cleft palate, sensorineural hearing loss, and supernumerary flexion creases†‡

We report on two daughters and a son of a Thai family who were affected with BWS. Their clinical findings consist of cleft palate, omphalocele, anterior ear creases, indented lesions on the posterior rim of the helix, macroglossia, posterior crossbite, and anterior open bite. The younger daughter and son had newly recognized findings of the BWS including sensorineural hearing loss and supernumerary flexion creases of the fingers. A novel mutation in CDKN1C (c.579delT; p.A193AfsX46) was found in all affected individuals and their mother. This mutation is located in the central highly polymorphic hexanucleotide repeat encoding a proline‐alanine series of repeats (PAPA‐domain). This domain is involved in MAP kinase phosphorylation. This is for the first time that sensorineural hearing loss and supernumerary flexion creases of the fingers are associated with mutation in CDKN1C.