Ricardo Gracia

Analysis of steroid 21-hydroxylase gene mutations in the Spanish population

Steroid 21 -hydroxylase deficiency is the major cause of congenital adrenal hyperplasia. Genotyping for deletions and nine point mutations in the CYP21 gene has been performed in 38 Spanish patients and their relatives by Southern blot analysis and allele-specific oligonucleotide hybridization. Three clinical variants were included in this study, viz., salt-wasting (SW, 21 patients), simple virilizer (SV, two patients), and late-onset (LO, 15 patients) forms. Twenty-three patient genotypes (16 SW, two SV, and five LO) were fully characterized. In both alleles, all but one of these severe forms (SW and SV) presented mutations that abolished or severely affected enzymatic activity. Patients with LO forms showed mutations that moderately impaired enzymatic activity in both alleles, or severe mutations in only one chromosome. Of 46 chromosomes from severe forms, 41 were characterized in this study (89%). The most frequent mutation was an aberrant splicing site (655 A or C to G) in intron 2, in 30% of these chromosomes. Deletions were found in 20%, and large gene conversions in 13% of these alleles. This screening allowed the characterization of 18 out of 30 LO chromosomes, the most frequent mutation being Val281Leu (37%). Severe mutations were found, in heterozygosis, in one third of LO patients.

Identification of the first recurrent PAR1 deletion in Léri-Weill dyschondrosteosis and idiopathic short stature reveals the presence of a novel SHOX enhancer

Background SHOX, located in the pseudoautosomal region 1 (PAR1) of the sexual chromosomes, encodes a transcription factor implicated in human growth. Defects in SHOX or its enhancers have been observed in ∼60% of Leri-Weill dyschondrosteosis (LWD) patients, a skeletal dysplasia characterised by short stature and/or the characteristic Madelung deformity, and in 2–5% of idiopathic short stature (ISS). To identify the molecular defect in the remaining genetically undiagnosed LWD and ISS patients, this study screened previously unanalysed PAR1 regions in 124 LWD and 576 ISS probands. Methods PAR1 screening was undertaken by multiplex ligation dependent probe amplification (MLPA). Copy number alterations were subsequently confirmed and delimited by locus-specific custom-designed MLPA, array comparative genomic hybridisation (CGH) and breakpoint junction PCR/sequencing. Results A recurrent PAR1 deletion downstream of SHOX spanning 47543 bp with identical breakpoints was identified in 19 LWD (15.3%) and 11 ISS (1.9%) probands, from 30 unrelated families. Eight evolutionarily conserved regions (ECRs 1–8) identified within the deleted sequence were evaluated for SHOX regulatory activity by means of chromosome conformation capture (3C) in chicken embryo limbs and luciferase reporter assays in human U2OS osteosarcoma cells. The 3C assay indicated potential SHOX regulatory activity by ECR1, which was subsequently confirmed to act as a SHOX enhancer, operating in an orientation and position independent manner, in human U2OS cells. Conclusions This study has identified the first recurrent PAR1 deletion in LWD and ISS, which results in the loss of a previously uncharacterised SHOX enhancer. The loss of this enhancer may decrease SHOX transcription, resulting in LWD or ISS due to SHOX haploinsufficiency.

Macrocephaly–capillary malformation: Analysis of 13 patients and review of the diagnostic criteria

Macrocephaly–capillary malformation (M‐CM) is a genetic syndrome of unknown etiology characterized by an enlarged head circumference and patchy, reticular capillary malformation. We describe the clinical features of 13 cases, report on the genome‐wide Copy Number Variation characterization of these patients, analyze the main clinical features of this syndrome and propose a modification of the current diagnostic criteria: the inclusion of both overgrowth/asymmetry and neuroimaging alterations as major criteria.

Primary Acid-Labile Subunit Deficiency due to Recessive IGFALS Mutations Results in Postnatal Growth Deficit Associated with Low Circulating Insulin Growth Factor (IGF)-I, IGF Binding Protein-3 Levels, and Hyperinsulinemia

CONTEXT Up to 90% of circulating IGF-I and IGF-II are carried bound to either IGF binding protein (IGFBP)-3 or IGFBP-5 and the acid-labile subunit (ALS) in the form of tertiary complexes that extend their circulating half-life. Three cases of complete ALS deficiency have been recently reported in short-stature patients with very low circulating IGF-I and IGFBP-3 levels who presented with homozygous or compound heterozygous mutations in the ALS encoding gene (IGFALS; 16p13.3), thus supporting a role for ALS in the regulation of the bioavailability of IGFs during postnatal growth. OBJECTIVE We present the molecular and clinical characterization of two novel IGFALS mutations that caused complete ALS deficiency in three unrelated patients with postnatal growth deficit, low IGF-I and IGFBP-3 levels, and no GH deficiency. RESULTS IGFALS mutation screening identified a novel homozygous IGFALS missense mutation, which altered a conserved residue, N276S, in two of the probands. The third proband presented a novel homozygous nonsense mutation, Q320X, that is predicted to generate a severely truncated ALS protein. The affected probands presented a similar phenotype characterized by a moderate postnatal growth deficit associated with undetectable ALS, low IGF-I, IGF-II, and IGFBP-3, and hyperinsulinemia, and, in two cases, delayed puberty. CONCLUSIONS Primary ALS deficiency due to IGFALS mutations should be considered as a possible cause of postnatal growth deficit in IGF-I-deficient patients in the absence of GH deficiency or insensitivity. Determination of serum ALS levels and basal insulinemia can be helpful in the differential diagnosis of patients with idiopathic IGF-I deficiency.

Identification of the first PAR1 deletion encompassing upstream SHOX enhancers in a family with idiopathic short stature

Short stature homeobox-containing gene, MIM 312865 (SHOX) is located within the pseudoautosomal region 1 (PAR1) of the sex chromosomes. Mutations in SHOX or its downstream transcriptional regulatory elements represent the underlying molecular defect in ∼60% of Léri-Weill dyschondrosteosis (LWD) and ∼5–15% of idiopathic short stature (ISS) patients. Recently, three novel enhancer elements have been identified upstream of SHOX but to date, no PAR1 deletions upstream of SHOX have been observed that only encompass these enhancers in LWD or ISS patients. We set out to search for genetic alterations of the upstream SHOX regulatory elements in 63 LWD and 100 ISS patients with no known alteration in SHOX or the downstream enhancer regions using a specifically designed MLPA assay, which covers the PAR1 upstream of SHOX. An upstream SHOX deletion was identified in an ISS proband and her affected father. The deletion was confirmed and delimited by array-CGH, to extend ∼286 kb. The deletion included two of the upstream SHOX enhancers without affecting SHOX. The 13.3-year-old proband had proportionate short stature with normal GH and IGF-I levels. In conclusion, we have identified the first PAR1 deletion encompassing only the upstream SHOX transcription regulatory elements in a family with ISS. The loss of these elements may result in SHOX haploinsufficiency because of decreased SHOX transcription. Therefore, this upstream region should be included in the routine analysis of PAR1 in patients with LWD, LMD and ISS.

CDKN1C Mutations in HELLP/Preeclamptic Mothers of Beckwith–Wiedemann Syndrome (BWS) Patients

Preeclampsia is the development of new-onset hypertension with proteinuria after 20 weeks of gestation. HELLP syndrome (haemolysis, elevated liver enzymes, and low platelet count) is a severe form of preeclampsia with high rates of neonatal and maternal morbidity. In recent years, loss of function of cdkn1c (a tight-binding inhibitor of G1 cyclin/cyclin-dependent kinase complexes and a negative regulator of cell proliferation) has been observed in several mouse models of preeclampsia. In this paper, we report on three women with HELLP/preeclampsia who had children with Beckwith Wiedemann syndrome, a complex genetic disorder characterised, among other findings, by overgrowth, omphalocele and macroglossia. All three children displayed mutations in CDKN1C predicted to generate truncated proteins. Two of the mutations were maternally inherited while the third was de novo. This finding suggests a fetal contribution to the maternal disease. To the best of our knowledge this is the first report of CDKN1C mutations in children born to women with preeclampsia/HELLP syndrome, thus suggesting the involvement of an imprinted gene in the pathophysiology of preeclampsia.

Constitutional mosaic genome-wide uniparental disomy due to diploidisation: an unusual cancer-predisposing mechanism

Molecular studies in a patient with Beckwith–Wiedemann syndrome phenotype who developed two different tumours revealed an unexpected observation of almost complete loss of heterozygosity of all chromosomes. It is shown, by means of numerous molecular methods, that the absence of maternal contribution in somatic cells is due to high-degree (∼85%) genome-wide paternal uniparental disomy (UPD). The observations indicate that the genome-wide UPD results from diploidisation, and have important implications for genetic counselling and tumour surveillance for the growing number of UPD associated imprinting disorders.

Clinical and molecular studies on two further families with simpson-golabi-behmel syndrome

The Simpson‐Golabi‐Behmel syndrome (SGBS) (OMIM 312870) is an overgrowth/multiple congenital anomalies syndrome caused by a semi‐dominant X‐linked gene encoding glypican 3 (GPC3). It shows great clinical variability, ranging from mild forms in carrier females to lethal forms with failure to thrive in males. The most consistent findings in SGBS are pre‐ and postnatal macrosomia, characteristic facial anomalies and abnormalities affecting the internal organs, skeleton, and on some occasions, mental retardation of variable degree. SGBS is also associated with an increased risk of developing embryonal tumors, mostly Wilms and liver tumors. We describe two molecularly‐confirmed families with SGBS. All patients had typical manifestations of SGBS including some female relatives who had minor manifestations of the disorder. Some patients had novel findings such as a deep V‐shaped sella turcica and six lumbar vertebrae. Molecular studies in affected patients showed a deletion of exon 6 in family 1 and an intronic mutation in family 2.

Microsatellite markers in the indirect analysis of the steroid 21-hydroxylase gene.

Prenatal diagnosis and treatment of congenital adrenal hyperplasia due to steroid 21‐hydroxylase (21‐OH) deficiency has been proved to be effective. Screening for a panel of nine point mutations, deletions, and gene conversions allows the identification of most of the mutations, although 6–12 per cent of chromosomes remain uncharacterized. In the present study, microsatellite typing in the HLA region was performed in 23 21‐OH deficiency families to determine the usefulness of these markers in the indirect identification of disease alleles. Two Génèthon markers (D6S273 and D6S439) in the HLA complex, class III and II regions in 5′ and 3′, respectively to the CYP21 gene, were typed together with a microsatellite at intron 3 of the TAP1 gene also in 3′. The heterozygosity of these markers provided informativity in all but one family, in which only the father was informative. Direct genotyping of the chromosomes confirmed in each case the correct assignment of the disease alleles in the sibling. The indirect analysis of the 21‐OH gene through D6S273, TAP1, and D6S439 microsatellites provides useful information in the molecular analysis of steroid 21‐OH deficiency.

The G397A (E133K) change in the AGGF1 (VG5Q) gene is a single nucleotide polymorphism in the Spanish population

Silvia Gutierrez, Luis Magano, Alicia Delicado, Marı́a A. Mori, Marı́a L. de Torres, Luis Fernández, Marı́a Palomares, Eva Fernández, Gemma R. Tarduchy, Jesús Molano, Ricardo Gracia, Isidora López Pajares, and Pablo Lapunzina* Department of Molecular Genetics, Hospital Universitario La Paz, Madrid, Spain Department of Medical Genetics, Hospital Universitario La Paz, Madrid, Spain Sequencing Unit, IBB, Madrid, Spain The Spanish Overgrowth Syndrome Registry