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Renpenning syndrome (OMIM: 309500) is a rare X-linked disorder that causes intellectual disability, microcephaly, short stature, a variety of eye anomalies, and characteristic craniofacial features. This condition results from pathogenic variation of PQBP1, a polyglutamine-binding protein involved in transcription and pre-mRNA splicing. Renpenning syndrome has only been reported in affected males. Carrier females do not usually have clinical features, and in reported families with Renpenning syndrome, most female carriers exhibit favorable skewing of X-chromosome inactivation. We describe a female with syndromic features typical of Renpenning syndrome. She was identified by exome sequencing to have a de novo heterozygous c.459_462delAGAG mutation in PQBP1 (Xp11.23), affecting the AG hexamer in exon 4, which is the most common causative mutation in this syndrome. Streaky hypopigmentation of the skin was observed, supporting a hypothesized presence of an actively expressed, PQBP1 mutation-bearing X-chromosome in some cells. X-inactivation studies on peripheral blood cells demonstrated complete skewing in both the proband and her mother with preferential inactivation of the maternal X chromosome in the child. We demonstrated expression of the PQBP1 mutant transcript in leukocytes of the affected girl. Therefore, it is highly likely that the PQBP1 mutation arose from the paternal X chromosome., (© 2019 Wiley Periodicals, Inc.)

Pseudohypoparathyrodism (PHP) is a disorder caused by mutations in the guanine nucleotide-binding α-subunit (GNAS). We sought to determine the genetic origin of PHP1a in one affected family. We identified the previously reported Gsα R231H mutation in family members affected with PHP1a. DNA analysis found that the two clinically affected sons are heterozygous for the mutation. The sons have PHP1a, manifesting obesity, intellectual disability, hypogonadism, hypothyroidism and elevated PTH levels. Initial DNA sequencing did not detect the mutation in either parent. However, their mother displayed some features of PHP, including elevated PTH levels and asymmetrical metacarpal shortening. Using molecular cloning, we detected the mutation at low levels in the mother's leukocyte DNA, consistent with somatic mosaicism and her mildly affected status. Thus, we have identified additional cases of PHP1a caused by the Gsα R231H mutation. In this family, the mother has a milder phenotype due in part to somatic mosaicism, whereas the two affected sons have full PHP1a. Though somatic mosaicism for activating GNAS mutations is known to occur in McCune-Albright syndrome, this is the first report confirming somatic mosaicism for a hypofunctioning GNAS mutation in a PHP kindred., (© 2010 Wiley-Liss, Inc.)

We report on a 14-year-old boy who presented with bilateral cleft lip and palate, hearing loss, a language processing disorder, and mild mental retardation (MR). G-banded chromosome analysis of the patient and his family revealed he carried an apparently balanced de novo complex translocation involving chromosomes 5, 6, and 7. Chromosomal comparative genomic hybridization (CGH) was performed to investigate the possibility of any genomic imbalance as a result of the complex rearrangement. No abnormality was detected at any of the translocation breakpoint regions (5p13.2, 6p24, 7q21.1, and 7q21.3), nor was there any other imbalance which fell inside our significance level of 0.8-1.2. Array-CGH analysis was initiated to perform a higher resolution search for gains and losses, and revealed a deletion of two adjacent clones, CTB-133K23 and RP11-112P4, mapping to 7q31.3, which are 4.4 Mb apart. Fluorescence in situ hybridization (FISH) using these two clones confirmed the deletion. 7q31 has frequently been implicated in the search for genes involved in speech and language disorders. The specific 7q31.3 region deleted in our patient has significant overlap with some such areas of the genome. These findings are, therefore, of value in identifying genes involved in the speech and language phenotypes. This study has shown the importance of array-CGH in investigating patients who have clinical features suggestive of a chromosome abnormality, but with apparently balanced chromosome rearrangements. It has demonstrated that the array-CGH technique provides a much greater insight into submicroscopic chromosome imbalances than conventional cytogenetic techniques.