Characterization of a 8q21.11 microdeletion syndrome associated with intellectual disability and a recognizable phenotype.

We report eight unrelated individuals with intellectual disability and overlapping submicroscopic deletions of 8q21.11 (0.66-13.55 Mb in size). The deletion was familial in one and simplex in seven individuals. The phenotype was remarkably similar and consisted of a round face with full cheeks, a high forehead, ptosis, cornea opacities, an underdeveloped alae, a short philtrum, a cupid's bow of the upper lip, down-turned corners of the mouth, micrognathia, low-set and prominent ears, and mild finger and toe anomalies (camptodactyly, syndactyly, and broadening of the first rays). Intellectual disability, hypotonia, decreased balance, sensorineural hearing loss, and unusual behavior were frequently observed. A high-resolution oligonucleotide array showed different proximal and distal breakpoints in all of the individuals. Sequencing studies in three of the individuals revealed that proximal and distal breakpoints were located in unique sequences with no apparent homology. The smallest region of overlap was a 539.7 kb interval encompassing three genes: a Zinc Finger Homeobox 4 (ZFHX4), one microRNA of unknown function, and one nonfunctional pseudogen. ZFHX4 encodes a transcription factor expressed in the adult human brain, skeletal muscle, and liver. It has been suggested as a candidate gene for congenital bilateral isolated ptosis. Our results suggest that the 8q21.11 submicroscopic deletion represents a clinically recognizable entity and that a haploinsufficient gene or genes within the minimal deletion region could underlie this syndrome.

Haploinsufficiency of BMP4 gene may be the underlying cause of Frías syndrome.

In 2005, we reported on a family as having Frías syndrome (OMIM: 609640), with four affected members displaying a pattern of congenital defects nearly identical to those observed in a mother and son described by Frias [Frías et al. (1975). Birth Defects Orig Artic Ser 11:30-33]. These defects included growth deficiency, facial anomalies, and hand and foot alterations. We had the opportunity to study this family again due to the birth of another affected girl, who presented with similar facial characteristics to those of her elder half-sister and the rest of affected relatives, which consisted of mild exophthalmia, bilateral palpebral ptosis, downslanting palpebral fissures, and hypertelorism. We performed array-CGH, which identified an identical interstitial deletion of chromosome 14q22.1-q22.3 in the mother and two daughters. The deletion is 4.06 Mb in length and includes the BMP4 gene, a member of the bone morphogenetic protein (BMP) family of secreted proteins. A review of the literature showed that deletions or mutations of this gene underlie congenital defects affecting brain, eye, teeth, and digit development. Although the clinical manifestations of the current family correlate with the defects observed in patients having either 14q22-q23 deletions or mutations of BMP4, they show a milder phenotype. In order to understand the clinical variability, we evaluated the already known functional characteristics of the BMP gene members. This gene family plays an important role during early embryogenesis, and the complex synergistic functions and redundancies of the BMPs led us to conclude that haploinsufficiency of BMP4 is likely to be responsible for the clinical expression of Frías syndrome.

A 2.84 Mb deletion at 21q22.11 in a patient clinically diagnosed with Marden-Walker syndrome.

We present a girl with the characteristic clinical picture associated with Marden-Walker syndrome (MWS; OMIM 248700), including mask-like face with blepharophimosis, joint contractures, intellectual disability, a multicystic dysplastic kidney and cerebral dysgenesis. The long-term follow-up allowed us to monitor the evolution of the phenotype in this patient, and among the main findings we highlight the following: demyelination of the pyramidal tract demonstrated by transcranial magnetic stimulation and the involvement of the levator muscles of angle of mouth in fixed facial expression with relative integrity of the rest of the facial expression muscles. A 244 k array comparative genomic hybridization (aCGH) was carried out and showed a de novo interstitial deletion of approximately 2.84 Mb affecting only the cytoband 21q22.11 (genome coordinates chr21:31,874,016-34,711,763). We selected 10 of the most recent published cases with either total or partial deletions of cytoband 21q22.11 that provided good characterization of the genomic size or the genes in the deleted regions. We observed that in nine of the 10 cases the deleted regions included the RUNX1 gene in 21q22.12, which is not affected in the current patient's deletion or in that of Patient 3 from Roberson et al. [2011]. After a comparison of shared deleted genes between cases, and correlation of their potential phenotypes, we concluded that the pattern of defects considered for a diagnosis of MWS may represent part of the phenotypic expression of a partial or total deletion of 21q22.11.