Andreina Cattani

A Unique Insertion/Substitution in Helix H1 of the Vitamin D Receptor Ligand Binding Domain in a Patient With Hereditary 1,25‐Dihydroxyvitamin D‐Resistant Rickets

A young Chilean boy with severe rickets was found to have hereditary vitamin D‐resistant rickets without alopecia. He had a unique insertion/substitution mutation in the ligand‐binding domain of the vitamin D receptor. The in‐frame mutation disrupted ligand binding and co‐activator binding and resulted in 1,25(OH)2D3 resistance.

A Novel Adrenocorticotropin Receptor Mutation Alters Its Structure and Function, Causing Familial Glucocorticoid Deficiency

CONTEXT Familial glucocorticoid deficiency (FGD) is an autosomal recessive disorder characterized by unresponsiveness to ACTH. In this study, two mutations of the ACTH receptor (MC2R) gene are reported in this FGD clinical case. OBJECTIVE The objective of the study was to characterize a novel MC2R gene mutation in a compound heterozygous patient with FGD phenotype. DESIGN This was a clinical case description, biochemical, molecular, and bioinformatics analysis to describe a novel MC2R gene mutation. PATIENTS The subject of the study was a male diagnosed with primary adrenal insufficiency. The family history showed nonconsanguineous healthy parents, three healthy siblings, and one brother affected with FGD. MAIN OUTCOME MEASURES The mutant MC2R-Ala126Ser showed significantly lower activity when it was stimulated with ACTH-(1-24) than did cells transfected with wild-type MC2R. RESULTS The molecular studies demonstrated the presence of an adenine heterozygous insertion (InsA1347) in the MC2R gene (G217fs) in the patient. This insertion was due to a frame shift mutation in one allele and a premature stop codon codifying an aberrant receptor of 247 residues (27.2 kDa). We also found a novel heterozygous mutation alanine 126 by serine. Molecular dynamic simulations showed that serine 126 side chain fluctuates forming a noncanonical intrahelical hydrogen bond in the transmembrane helix 3 of the mutated receptor. This produces a structural rearrangement of the MC2R internal cavities that may affect the ligand recognition and signal transduction throughout the G protein. CONCLUSIONS We propose a molecular explanation for the reduced activity exhibited by the MC2R alanine 126 by serine mutant.

Mutations in the CYP21B gene in a Chilean population with simple virilizing congenital adrenal hyperplasia

Steroid 21-hydroxylase deficiency (21OHD) compromises about 95% of all cases of congenital adrenal hyperplasia. We have characterized the disease-causing mutations in the steroid 21-hydroxylase genes of 19 Chilean patients (12 females and 7 males) with the simple virilizing (SV) form of 21OHD and compared them with other SV-populations. Using allele-specific polymerase chain reaction, we identified lesions in 28 chromosomes out of 38 tested (73.7%). The most frequent finding was the mutation I173N= 12/38 (31.6%) similar as described in Caucasian, Asian and other Hispanic populations, where this mutation represents around 20–40% of the genetic defects in the CYP21B gene. The mutation V282L=4/38 (10.5%) and deletion (Del) or large gene conversion (LGC)=3/38 (7.9%) were also frequently detected. Only 2 alleles carried the mutation I2 splice (5.3%), this frequency is lower than that reported in Caucasian or in Mexican populations. We did not find alleles with the mutations R357W, Cluster E6, P31L and P454S in these patients. The complete genotype was determined in 11/19 patients (58%) and one allele in 6/19 patients (31.6%). In summary, about 30% of the Chilean population with SV 21OHD presented the missense mutation I173N as described in other populations. The frequency of the other lesions showed differences even between populations with similar genetic background.

A novel GNAS mutation in an infant boy with pseudohypoparathyroidism type Ia and normal serum calcium and phosphate levels

The objective of this study was to describe a new mutation in GNAS in a family with pseudohypoparathyroidism type Ia (PHP Ia), a rare osteometabolic disease. An 8-month-old boy was seen by an Endocrinologist due to obesity and low growth velocity. Noteworthy, his mother exhibited typical Albright hereditary osteodystrophy (AHO) phenotype. The clinical diagnosis of PHP Ia was suspected. The GNAS coding region from mother and son was amplified and directly sequenced. A novel heterozygous missense mutation (c.673T>C) was identified in exon 5 in both patients. In this family, the mothers clinical picture was the clue for the sons diagnosis. Molecular analysis of GNAS confirmed the diagnosis of PHP Ia in both patients and the childs early diagnosis was possible. Moreover, this novel missense substitution expands the spectrum of GNAS mutations associated with this disorder and allows for genetic counseling of this family.

Marcadores de inflamación endotelial subclínica en una familia con hiperaldosteronismo familiar tipo I por mutación de novo

Type I familial hyperaldosteronism is caused by thepresence of a chimaeric gene CYP11B1/CYP11B2 which encodes an enzyme with aldosteronesynthetase activity regulated by adrenocorticotrophic hormone (ACTH). Therefore, in patients with FH-I is possible to normalize the aldosterone levels with glucocorticoid treatment. Recently it has beenshown that aldosterone plays a role in the production of endothelial oxidative stress and subclinicalinflammation.

A novel insertion in the FOXL2 gene in a Chilean patient with blepharophimosis ptosis epicanthus inversus syndrome type I

Abstract Objective: A novel insertion in the forkhead transcription factor 2 (FOXL2) was identified in a Chilean patient with blepharophimosis, ptosis, and epicanthus inversus syndrome associated with premature ovarian failure (BPES type I). A clinical and molecular characterization of a patient with BPES type I was performed. Method: We present a 16-year-old adolescent girl with surgically treated blepharophimosis, ptosis, and epicanthus inversus that was associated with delayed puberty and secondary amenorrhea at the age of 15, indicators that suggested that the patient had BPES type I. The FOXL2 gene was analyzed by sequencing its coding region. Results: The sequence analysis of the FOXL2 gene revealed a novel heterozygous mutation: an 11 bp duplication (c.901_911dup11) that was predicted to encode a truncated protein (p.Pro305Argfs*54). Conclusions: A novel out-of-frame duplication following the polyalanine domain in the FOXL2 gene was identified in a Chilean patient with BPES type I. This study characterized the molecular alterations in FOXL2 and confirmed the diagnosis, thereby providing information to allow for improved genetic counseling for the patient and her family.

The paradoxical response of growth hormone (GH) to thyrotropin-releasing hormone (TRH) in constitutionally tall children involves a cholinergic pathway.

To investigate whether or not a cholinergic pathway is involved in the paradoxical response of GH to TRH in constitutionally tall children, we studied 8 healthy prepubertal children aged

A126: Clusters of Autoimmune Diseases in Children and the Role of PTPN22 C1858T Gene Polymorphism in Pediatric Polyautoimmunity

4^{2}/{_{_{12}}} - 7^{10}/{_{_{12}}} {⤪ yr}

Molecular Characterization of Intron 2 Alternative Splicing As A Cause of the Classic Type of 21-Hydroxilase Deficit in Chile 33

, whose heights were over the 95th percentile of the NCHS tables. We defined as “paradoxical” a GH increment greater than 5 ng/ml in response to TRH. Five out of 8 children showed a paradoxical response of GH to TRH (mean GH peak after TRH of 10.7 ± 1.1 ng/ml). Pretreatment with atropine (0.01 mg/kg IM 30 min prior to the TRH administration) abolished the TRH induced GH rise (peak GH after TRH of 1.5 ± 1.0 ng/ml, p < 0.01) but did not modify the TSH response (peak TSH after TRH: basal conditions 8.7 ± 0.8 μU/ml, post atropine: 9.5 ± 1.4 μU/ml, p > 0.05). Our results demonstrate that a cholinergic pathway is involved in the paradoxical response of GH to TRH in constitutionally tall children.

VITAMIN D DEPENDENT RICKETS TYPE II (VDR-11). RESPONSE TO PROLONGED THERAPY WITH NOCTURNAL CALCIUM INFUSIONS

Autoimmune diseases (AIDs) have familial aggregation and frequently share a common genetic background, but few studies have evaluated autoimmune clusters in children with AIDs and their families. Children with more than one AID (pediatric polyautoimmunity) may have a stronger genetic component than children with a single AID. The objectives of this study were to identify clusters of AIDs in children and their first‐degree relatives and to evaluate the association of PTPN22 C1858T gene polymorphism with pediatric polyautoimmunity.