PITX2C loss-of-function mutations responsible for idiopathic atrial fibrillation

OBJECTIVE: This study aimed to identify novel PITX2c mutations responsible for idiopathic atrial fibrillation. METHODS: A cohort of 210 unrelated patients with idiopathic atrial fibrillation and 200 unrelated, ethnically matched healthy individuals used as controls were recruited. The whole coding exons and splice junctions of the PITX2c gene, which encodes a paired-like homeobox transcription factor required for normal cardiovascular morphogenesis, were sequenced in 210 patients and 200 control subjects. The causative potentials of the identified mutations were automatically predicted by MutationTaster and PolyPhen-2. The functional characteristics of the PITX2c mutations were explored using a dual-luciferase reporter assay system. RESULTS: Two novel heterozygous PITX2c mutations (p.Q105L and p.R122C) were identified in 2 of the 210 unrelated patients with idiopathic atrial fibrillation. These missense mutations were absent in the 400 control chromosomes and were both predicted to be pathogenic. Multiple alignments of PITX2c protein sequences across various species showed that the altered amino acids were highly evolutionarily conserved. A functional analysis demonstrated that the mutant PITX2c proteins were both associated with significantly reduced transcriptional activity compared with their wild-type counterparts. CONCLUSION: The findings of this study associate PITX2c loss-of-function mutations with atrial fibrillation, supporting the hypothesis that dysfunctional PITX2c confers enhanced susceptibility to atrial fibrillation and suggesting potential implications for early prophylaxis and allele-specific therapy for this common arrhythmia. .

Lissencephaly, abnormal genitalia and refractory epilepsy: case report of XLAG syndrome / Lisencefalia, genitália ambígua e epilepsia refratária: relato de caso da síndrome XLAG

INTRODUCTION: X-linked lissencephaly with ambiguous genitalia (XLAG) is a recently described genetic disorder caused by mutation in the aristaless-related homeobox (ARX) gene (Xp22.13). Patients present with lissencephaly, agenesis of the corpus callosum, refractory epilepsy of neonatal onset, acquired microcephaly and male genotype with ambiguous genitalia. CASE REPORT: Second child born to healthy nonconsanguineous parents, presented with seizures within the first hour of life that remained refractory to phenobarbital, phenytoin and midazolam. Examination identified microcephaly, axial hypotonia, pyramidal signs and ambiguous genitalia. EEG showed disorganized background activity and seizures starting at the right midtemporal, central and occipital regions. MRI showed diffuse pachygyria, moderate thickening of the cortex, enlarged ventricles, agenesis of the corpus callosum and septum pellucidum. Karyotype showed a 46,XY genotype. Additional findings were hypercalciuria, vesicoureteral reflux, patent ductus arteriosus and chronic diarrhea.

INTRODUÇÃO: Lisencefalia com genitália ambígua ligada ao X (XLAG) é doença genética recentemente descrita, causada por mutação no gene aristaless-related homeobox (ARX) (Xp22.13). Os pacientes apresentam lisencefalia, agenesia de corpo caloso, epilepsia refratária com início no período neonatal, microcefalia adquirida e genótipo masculino com genitália ambígua. RELATO DE CASO: Segundo filho de pais não-consangüíneos, apresentou crises na primeira hora de vida que permaneceram refratárias a fenobarbital, fenitoína e midazolam. Apresentava microcefalia, hipotonia axial, sinais de liberação piramidal e genitália ambígua. EEG demonstrou atividade de base desorganizada, crises convulsivas com início nas regiões temporal-média, central e occipital direitas. RNM demonstrou paquigiria difusa, moderado espessamento do córtex, ventrículos aumentados, agenesia de corpo caloso e septo pelúcido. Cariótipo evidenciou genótipo 46,XY. Achados adicionais foram: hipercalciúria, refluxo vésico-ureteral, ducto arterioso persistente e diarréia crônica.