Frameshift Mutation in Polar Rich Domain (PRD) of PQBP1 Gene Associated with Asymmetric Cerebellar Hemispheres: A Case Report of Renpenning Syndrome

Introduction: In 1962, Renpenning et al. published an article with 20 male patients from three generations with mental retardation. Scientists suggested that the syndrome with mutation mapped to the locus Xp11.2-p11.4 should be called Renpenning syndrome. The deletion/duplication of an AG dinucleotide on proximal Xp in the polyglutamine tract-binding protein 1 (PQBP1) gene causing frameshift in the fourth coding exon was identified as the most frequent mutation in this syndrome. Renpenning syndrome with asymmetric cerebellar hemispheres has not been reported previously. Case Presentation: In this case report, we presented an 11-year-old male with mild developmental delay and mild intellectual disability, microcephaly, dysmorphic face, short stature, and seizures. The following morphological abnormalities were detected: a wide nasal bridge, midfacial hypoplasia, short philtrum, low-set ears, low hanging columella, high palate, and narrow face. Neurological examination showed upper and lower extremities hypotonia with joint hypermobility. The patient had his first seizure at the age of seven, and he experienced a total of 10 seizures by the age 11. A systolic murmur of intensity 2/6 was present, and echocardiography showed chordae tendineae abnormalities in the left ventricle. Brain magnetic resonance imaging (MRI) showed asymmetric cerebellar hemispheres (mild right cerebellar hemisphere hypoplasia). A frameshift mutation in the polar reach domain (PRD) of the PQBP1 gene (c.459-462 delAGAG) was detected by exome sequencing. Conclusions: We showed the first case of genetically confirmed Renpenning syndrome in Serbia. Our patient had classical clinical manifestations for Renpenning syndrome as a consequence of frameshift mutation in the PRD of the PQBP1 gene. To the best of our knowledge, according to the literature, this is the first patient with Renpenning syndrome with asymmetric cerebellar hemispheres (mild right cerebellar hemisphere hypoplasia).

Exposure to ethanol leads to midfacial hypoplasia in a zebrafish model of FASD via indirect interactions with the Shh pathway

Background Gene-environment interactions are likely to underlie most human birth defects. The most common known environmental contributor to birth defects is prenatal alcohol exposure. Fetal alcohol spectrum disorders (FASD) describe the full range of defects that result from prenatal alcohol exposure. Gene-ethanol interactions underlie susceptibility to FASD, but we lack a mechanistic understanding of these interactions. Here, we leverage the genetic tractability of zebrafish to address this problem. Results We first show that vangl2, a member of the Wnt/planar cell polarity (Wnt/PCP) pathway that mediates convergent extension movements, strongly interacts with ethanol during late blastula and early gastrula stages. Embryos mutant or heterozygous for vangl2 are sensitized to ethanol-induced midfacial hypoplasia. We performed single-embryo RNA-seq during early embryonic stages to assess individual variation in the transcriptional response to ethanol and determine the mechanism of the vangl2-ethanol interaction. To identify the pathway(s) that are disrupted by ethanol, we used these global changes in gene expression to identify small molecules that mimic the effects of ethanol via the Library of Integrated Network-based Cellular Signatures (LINCS L1000) dataset. Surprisingly, this dataset predicted that the Sonic Hedgehog (Shh) pathway inhibitor, cyclopamine, would mimic the effects of ethanol, despite ethanol not altering the expression levels of direct targets of Shh signaling. Indeed, we found that ethanol and cyclopamine strongly, but indirectly, interact to disrupt midfacial development. Ethanol also interacts with another Wnt/PCP pathway member, gpc4, and a chemical inhibitor of the Wnt/PCP pathway, blebbistatin, phenocopies the effect of ethanol. By characterizing membrane protrusions, we demonstrate that ethanol synergistically interacts with the loss of vangl2 to disrupt cell polarity required for convergent extension movements. Conclusions Our results show that the midfacial defects in ethanol-exposed vangl2 mutants are likely due to an indirect interaction between ethanol and the Shh pathway. Vangl2 functions as part of a signaling pathway that regulates coordinated cell movements during midfacial development. Ethanol exposure alters the position of a critical source of Shh signaling that separates the developing eye field into bilateral eyes, allowing the expansion of the midface. Collectively, our results shed light on the mechanism by which the most common teratogen can disrupt development.

Nasal Septum Deviation as the Consequence of BMP-Controlled Changes to Cartilage Properties

The nasal septum cartilage is a specialized hyaline cartilage important for normal midfacial growth. Abnormal midfacial growth is associated with midfacial hypoplasia and nasal septum deviation (NSD). However, the underlying genetics and associated functional consequences of these two anomalies are poorly understood. We have previously shown that loss of Bone Morphogenetic Protein 7 (BMP7) from neural crest (BMP7ncko) leads to midfacial hypoplasia and subsequent septum deviation. In this study we elucidate the cellular and molecular abnormalities underlying NSD using comparative gene expression, quantitative proteomics, and immunofluorescence analysis. We show that reduced cartilage growth and septum deviation are associated with acquisition of elastic cartilage markers and share similarities with osteoarthritis (OA) of the knee. The genetic reduction of BMP2 in BMP7ncko mice was sufficient to rescue NSD and suppress elastic cartilage markers. To our knowledge this investigation provides the first genetic example of an in vivo cartilage fate switch showing that this is controlled by the relative balance of BMP2 and BMP7. Cellular and molecular changes similar between NSD and knee OA suggest a related etiology underlying these cartilage abnormalities.

Does the Timing of 1-Stage Palatoplasty With Radical Muscle Dissection Effect Long-Term Midface Growth? A Single-Center Retrospective Analysis

Objective: To evaluate the long-term effect of timing of 1-stage palatoplasty on midfacial growth in patients with cleft lip and palate (CLP). Design: Retrospective observational cohort study. Study Setting: Institutional hospital. Patients: One hundred twelve patients with CLP who underwent palatoplasty and were divided into 3 groups: group I: operated between 9 and 11 months; group II: operated between 18 and 20 months; and group III: operated between 21 and 24 months. Interventions: All patients underwent von Langenbeck palatoplasty technique, which was converted to a Bardach 2-flap technique in case of any technical difficulties. The patients were followed up between 8 and 9 years when they reported for secondary alveolar bone grafting. Postsurgical cephalometric and dental casts measurements were taken for midfacial growth analysis. Main Outcome Measures: The cephalometric measures were analyzed for midfacial growth and compared within the groups. Results: Statistically significant difference ( P < .01) was found on comparing the cephalometric parameters such as sella–nasion–A point angle (SNA), A point–nasion–B point angle (ANB), n toperpendicular to point A (N-perpA), condylon to point A (Co-A), anterior nasal spine to posterior nasal spine (ANS-PNS), nasion to Anterior nasal spine (N-ANS), nasion to menton (N Me), and witts appraisal (Witt (AO-BO)) in group I when compared to both group II and group III patients, implying deficient midfacial growth in group I. No statistical difference was found in the cephalometric values between group II and group III. Group II had better cephalometric measurements than group III, showing better growth in group II than group III. Overall, there was less incidence of midfacial hypoplasia in patients treated between 18 and 20 months (group II). Conclusion: We conclude that palatal closure carried out at 18 to 20 months and 21 to 24 months is associated with better midfacial growth when compared to closure at 9 to 11 months. The best time to operate would be between 18 and 20 months to avoid speech disturbances. Midfacial growth can be greatly influenced by the timing of 1-stage palatoplasty.

The Chromatin Regulator Ankrd11 Controls Palate and Cranial Bone Development

Epigenetic and chromatin regulation of craniofacial development remains poorly understood. Ankyrin Repeat Domain 11 (ANKRD11) is a chromatin regulator that has previously been shown to control neural stem cell fates via modulation of histone acetylation. ANKRD11 gene variants, or microdeletions of the 16q24.3 chromosomal region encompassing the ANKRD11 gene, cause KBG syndrome, a rare autosomal dominant congenital disorder with variable neurodevelopmental and craniofacial involvement. Craniofacial abnormalities include a distinct facial gestalt, delayed bone age, tooth abnormalities, delayed fontanelle closure, and frequently cleft or submucosal palate. Despite this, the dramatic phenotype and precise role of ANKRD11 in embryonic craniofacial development remain unexplored. Quantitative analysis of 3D images of KBG syndromic subjects shows an overall reduction in the size of the middle and lower face. Here, we report that mice with heterozygous deletion of Ankrd11 in neural crest cells (Ankrd11nchet) display a mild midfacial hypoplasia including reduced midfacial width and a persistent open fontanelle, both of which mirror KBG syndrome patient facial phenotypes. Mice with a homozygous Ankrd11 deletion in neural crest cells (Ankrd11ncko) die at birth. They show increased severity of several clinical manifestations described for KBG syndrome, such as cleft palate, retrognathia, midfacial hypoplasia, and reduced calvarial growth. At E14.5, Ankrd11 expression in the craniofacial complex is closely associated with developing bony structures, while expression at birth is markedly decreased. Conditional deletion of Ankrd11 leads to a reduction in ossification of midfacial bones, with several ossification centers failing to expand and/or fuse. Intramembranous bones show features of delayed maturation, with bone remodeling severely curtailed at birth. Palatal shelves remain hypoplastic at all developmental stages, with a local reduction in proliferation at E13.5. Our study identifies Ankrd11 as a critical regulator of intramembranous ossification and palate development and suggests that Ankrd11nchet and Ankrd11ncko mice may serve as pre-clinical models for KBG syndrome in humans.

First person – Pranidhi Baddam

ABSTRACTFirst Person is a series of interviews with the first authors of a selection of papers published in Disease Models & Mechanisms, helping early-career researchers promote themselves alongside their papers. Pranidhi Baddam is first author on ‘Neural crest-specific loss of Bmp7 leads to midfacial hypoplasia, nasal airway obstruction and disordered breathing, modeling obstructive sleep apnea’, published in DMM. Pranidhi is a PhD student in the lab of Daniel Graf at the University of Alberta, Edmonton, Canada, investigating the contribution of different types of cartilage to midfacial growth.

Occlusal and Functional Improvement of Patients With Midfacial Hypoplasia Corrected Using Intraoral Tooth-Borne Mid-Maxillary Osteodistractors at Teaching Hospital-Karapitiya, Sri Lanka

Objective: Mid-maxillary osteodistraction (MMOD) is a novel technique. This study seeks to assess the occlusal and functional improvement of patients with midfacial hypoplasia secondary to cleft lip and palate. Design: This was done as a retrospective study at the Regional Cleft Centre of the Teaching Hospital-Karapitiya (THK). Participants: A total of 81 patient records were accessed on those who underwent MMOD with a tooth-borne intraoral device from January 1, 2007, to December 31, 2016, at THK. Methods: Records of the patients included pre- and post-treatment lateral cephalograms, study models, speech assessments, and photographs. Results: An advancement ranging from 5 to 12 mm (mean, 8.14 mm) was achieved in all patients; 80% (n = 63) and 87.65% (n = 71) showed improvement in consonant production and quality of speech. These were statistically significant (P < .05). With regard to the Peer Assessment Rating score assessing the occlusal improvement, 97.6% showed an improvement whereas only 2 patients showed no improvement. There was a significant improvement in sella (S), nasion (N), and point A (SNA) angle; point A, the nasion, and point B (ANB) angle; and the maxillary length over the treatment period (P < .05). The change in the ANB angle and maxillary length significantly differed between genders with males having a comparatively higher improvement. The profile improvements were noteworthy on the profile photographs. Conclusion: This relatively novel approach to maxillary advancement by maxillary distraction using a combined surgical and modified orthodontic technique has proven to be successful. This protocol and the technique have improved function, occlusion, and the aesthetics.

Molecular Basis for Craniofacial Phenotypes Caused by Sclerostin Deletion

Some genetic disorders are associated with distinctive facial features, which can aid in diagnosis. While considerable advances have been made in identifying causal genes, relatively little progress has been made toward understanding how a particular genotype results in a characteristic craniofacial phenotype. An example is sclerosteosis/van Buchem disease, which is caused by mutations in the Wnt inhibitor sclerostin (SOST). Affected patients have a high bone mass coupled with a distinctive appearance where the mandible is enlarged and the maxilla is foreshortened. Here, mice carrying a null mutation in Sost were analyzed using quantitative micro–computed tomographic (µCT) imaging and histomorphometric analyses to determine the extent to which the size and shape of craniofacial skeleton were altered. Sost−/− mice exhibited a significant increase in appositional bone growth, which increased the height and width of the mandible and reduced the diameters of foramina. In vivo fluorochrome labeling, histology, and immunohistochemical analyses indicated that excessive bone deposition in the premaxillary suture mesenchyme curtailed overall growth, leading to midfacial hypoplasia. The amount of bone extracellular matrix produced by Sost−/− cells was significantly increased; as a consequence, osteoid seams were evident throughout the facial skeleton. Collectively, these analyses revealed a remarkable fidelity between human characteristics of sclerosteosis/van Buchem disease and the Sost−/− phenotype and provide clues into the conserved role for sclerostin signaling in modulating craniofacial morphology.