RESUMO
Dozens of genes are associated with idiopathic hypogonadotropic hypogonadism (IHH) and an oligogenic etiology has been suggested. However, the associated genes may account for only approximately 50% cases. In addition, a genomic systematic pedigree analysis is still lacking. Here, we conducted whole exome sequencing (WES) on 18 unrelated men affected by IHH and their corresponding parents. Notably, one reported and 10 novel variants in eight known IHH causative genes (AXL, CCDC141, CHD7, DMXL2, FGFR1, PNPLA6, POLR3A, and PROKR2), nine variants in nine recently reported candidate genes (DCAF17, DCC, EGF, IGSF10, NOTCH1, PDE3A, RELN, SLIT2, and TRAPPC9), and four variants in four novel candidate genes for IHH (CCDC88C, CDON, GADL1, and SPRED3) were identified in 77.8% (14/18) of IHH cases. Among them, eight (8/18, 44.4%) cases carried more than one variant in IHH-related genes, supporting the oligogenic model. Interestingly, we found that those variants tended to be maternally inherited (maternal with n = 17 vs paternal with n = 7; P = 0.028). Our further retrospective investigation of published reports replicated the maternal bias (maternal with n = 46 vs paternal with n = 28; P = 0.024). Our study extended a variant spectrum for IHH and provided the first evidence that women are probably more tolerant to variants of IHH-related genes than men.
RESUMO
La microdeleción 16p11.2 se relaciona, habitualmente, con discapacidad intelectual y trastornos del espectro autista. El rango fenotípico incluye un espectro que se extiende desde discapacidad intelectual con o sin autismo, alteraciones del aprendizaje y del lenguaje hasta fenotipos normales. El diagnóstico de la microdeleción se realiza mediante estudios genómicos capaces de identificar variación en número de copias, como la hibridación genómica comparativa en microarreglos, conocida como arrayCGH. Sin embargo, la predicción del fenotipo de un individuo basada únicamente en la localización de dicha deleción sigue siendo un desafío, ya que la existencia de un gran número de variantes en el genoma dificulta la interpretación de posibles efectos funcionales de los genes que contribuyen a dicha región. Se describen dos casos clínicos de pacientes con microdeleción heterocigota en 16p11.2 y se destacan los hallazgos fenotípicos y conductuales que dificultaron la estrategia diagnóstica. También se discuten las implicancias del diagnóstico para el asesoramiento genético familiar.
The 16p11.2 recurrent microdeletion phenotype is characterized by developmental delay, intellectual disability, and/or autism spectrum disorder. This microdeletion is associated with variable clinical outcome, the phenotypical spectrum ranges from intellectual disability and/or multiple congenital anomalies, autism, learning and speech problems, to a normal phenotype. Genomic testing that determines copy number of sequences, such as chromosomal microarray, is used to identify this microdeletion. However, the prediction of the individual phenotype of a patient based only on the location of such deletion remains a challenge, regarding the existence of many genomic variants that might hinder the interpretation of possible functional effects between most of the contributing genes to that region. We describe the clinical findings in two subjects with heterozygous microdeletions at 16p11.2, highlighting the phenotypic and behavioural findings that conditioned the diagnostic strategy. We also discuss the implications of diagnosis, in practical counselling situations.