A recognizable phenotype related to 19p13.12 microdeletion

De novo missense variants in HDAC3 leading to epigenetic machinery dysfunction are associated with a variable neurodevelopmental disorder

Histone deacetylase 3 (HDAC3) is a crucial epigenetic modulator essential for various developmental and physiological functions. Although its dysfunction is increasingly recognized in abnormal phenotypes, to our knowledge, there have been no established reports of human diseases directly linked to HDAC3 dysfunction. Using trio exome sequencing and extensive phenotypic analysis, we correlated heterozygous de novo variants in HDAC3 with a neurodevelopmental disorder having variable clinical presentations, frequently associated with intellectual disability, developmental delay, epilepsy, and musculoskeletal abnormalities. In a cohort of six individuals, we identified missense variants in HDAC3 (c.277G>A [p.Asp93Asn], c.328G>A [p.Ala110Thr], c.601C>T [p.Pro201Ser], c. 797T>C [p.Leu266Ser], c.799G>A [p.Gly267Ser], and c.1075C>T [p.Arg359Cys]), all located in evolutionarily conserved sites and confirmed as de novo. Experimental studies identified defective deacetylation activity in the p.Asp93Asn, p.Pro201Ser, p.Leu266Ser, and p.Gly267Ser variants, positioned near the enzymatic pocket. In addition, proteomic analysis employing co-immunoprecipitation revealed that the disrupted interactions with molecules involved in the CoREST and NCoR complexes, particularly in the p.Ala110Thr variant, consist of a central pathogenic mechanism. Moreover, immunofluorescence analysis showed diminished nuclear to cytoplasmic fluorescence ratio in the p.Ala110Thr, p.Gly267Ser, and p.Arg359Cys variants, indicating impaired nuclear localization. Taken together, our study highlights that de novo missense variants in HDAC3 are associated with a broad spectrum of neurodevelopmental disorders, which emphasizes the complex role of HDAC3 in histone deacetylase activity, multi-protein complex interactions, and nuclear localization for proper physiological functions. These insights open new avenues for understanding the molecular mechanisms of HDAC3-related disorders and may inform future therapeutic strategies.

Prkra Mutation Alters mRNA Expression During Embryonic External Ear Development

To understand the changes in mRNA expression during the embryonic development of the external mouse ear after the point mutation of the Prkra gene, Prkra short ear mouse model was used to study the development of the embryonic external ear. The tissues of the embryonic external ear were obtained when mouse embryos developed to E15.5 and E17.5. The changes in the mRNA expression profile were detected and analyzed. Find_circ and CIRI2 softwares were used to identify the upregulated and down-regulated expression of mRNA in the experimental and control groups. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes functional annotations were conducted on the differentially expressed mRNA, and the related signal pathways were analyzed after the upregulation and down-regulation of mRNA expression. This study aimed to understand the regulation of mRNA expression in Prkra short-ear mice during the external ear development in embryos. The results showed a correlation between abnormally expressed mRNA and signal pathways and the regulation of the development of the external ear of Prkra short-ear mice, and there were differences in some key regulatory mRNA changes after the Prkra gene point mutation. This study will provide a new clue for the mechanism of mRNA regulating the development of the external mouse ear. The change in mRNA expression profile can also provide clues for studying the biological regulation mechanism of external ear embryonic development.

Microdeletions at 19p13.11p12 in five individuals with neurodevelopmental delay

Only few copy number variants at chromosome 19p13.11 have been reported, thus associated clinical information is scarce. Proximal to these copy number losses, we now identified deletions in five unrelated individuals with neurodevelopmental disorders. They presented with psychomotor delay as well as behavioral and sleeping disorders, while complex cardiovascular, skeletal, and various other malformations were more variable. Dysmorphic features were rather unspecific and not considered as a recognizable gestalt. Neither of the analyzed parents carried their offsprings' deletions, indicating de novo occurrence. The deletion sizes ranged between 0.7 and 5.2 Mb, were located between 18 and 24 megabases from the telomere, and contained a variable number of protein-coding genes (n = 25-68). Although not all microdeletions shared a common region, the smallest common overlap of some of the deletions provided interesting insights in the chromosomal region 19p13.11p12. Diligent literature review using OMIM and Pubmed did not identify a satisfying candidate gene for neurodevelopmental disorders. In the literature, a de novo in-frame deletion in MAU2 was considered pathogenic in an individual with Cornelia de Lange syndrome. Therefore, the clinical differential diagnosis of this latter syndrome in one individual and the encompassment of MAU2 in three individuals' deletions suggest clinical and genetic overlap with this specific syndrome. Three of the four here reported individuals with deletion encompassing GDF1 had different congenital heart defects, suggesting that this gene's haploinsufficiency might contribute to the cardiovascular phenotype, however, with reduced penetrance. Our findings indicate an association of microdeletions at 19p13.11/ 19p13.11p12 with neurodevelopmental disorders, variable symptoms, and malformations, and delineate the phenotypic spectrum of deletions within this genomic region.

Pathogenic Copy Number and Sequence Variants in Children Born SGA With Short Stature Without Imprinting Disorders

CONTEXT

Children born small-for-gestational-age with short stature (SGA-SS) is associated with (epi)genetic defects, including imprinting disorders (IDs), pathogenic copy number variants (PCNVs), and pathogenic variants of genes involved in growth. However, comprehensive studies evaluating these 3 factors are very limited.

OBJECTIVE

To clarify the contribution of PCNVs and candidate pathogenic variants to SGA-SS.

DESIGN

Comprehensive molecular analyses consisting of methylation analysis, copy number analysis, and multigene sequencing.

METHODS

We enrolled 140 patients referred to us for genetic testing for SGA-SS. Among them, we excluded 42 patients meeting Netchine-Harbison clinical scoring system criteria for Silver-Russell syndrome and 4 patients with abnormal methylation levels of the IDs-related differentially methylated regions. Consequently, we conducted copy number analysis and multigene sequencing for 86 SGA-SS patients with sufficient sample volume. We also evaluated clinical phenotypes of patients with PCNVs or candidate pathogenic variants.

RESULTS

We identified 8 (9.3%) and 11 (12.8%) patients with PCNVs and candidate pathogenic variants, respectively. According to the American College of Medical Genetics standards and guidelines, 5 variants were classified as pathogenic and the remaining 6 variants were classified as variants of unknown significance. Genetic diagnosis was made in 12 patients. All patients with PCNVs or candidate pathogenic variants did not correspond perfectly to characteristic clinical features of each specific genetic cause.

CONCLUSION

We clarified the contribution of PCNVs and pathogenic variants to SGA-SS without IDs. Comprehensive molecular analyses, including copy number analysis and multigene sequencing, should be considered for patients with unknown SGA-SS etiology.

Synophrys: The societal implications of the bad ol' unibrow

The complete or partial meeting of medial eyebrows at midline above the bridge of nose, forming a single band of hair, is known as synophrys or unibrow. With a few rare exceptions, when it may serve as a cutaneous marker lesion of several genetic disorders, with Cornelia De Lange syndrome being the commonest, synophrys is usually a normal variation. Although various cultures have prized synophrys as an attractive physical trait throughout history, in modern Western culture, the unibrow is frequently regarded as an undesirable and unappealing feature with negative connotations. Synophrys, derived from the Ancient Greek σύν (together, with) and ὀφρύς (eyebrow), meaning "with meeting eyebrows," refers to the complete or partial fusion of medial eyebrows at midline. The hair above the nasal bridge is often of the same color and thickness as the eyebrows, thus giving the appearance that they converge to form one uninterrupted line of hair, a single eyebrow.

Bromodomain Protein BRD4 Is Essential for Hair Cell Function and Survival

Hair cells (HCs) play crucial roles in perceiving sound, acceleration, and fluid motion. The tonotopic architecture of the sensory epithelium recognizes mechanical stimuli and convert them into electrical signals. The expression and regulation of the genes in the inner ear is very important to keep the sensory organ functional. Our study is the first to investigate the role of the epigenetic reader Brd4 in the mouse inner ear. We demonstrate that HC specific deletion of Brd4 in vivo in the mouse inner ear is sufficient to cause profound hearing loss (HL), degeneration of stereocilia, nerve fibers and HC loss postnatally in mouse; suggesting an important role in hearing function and maintenance.

Phenotype comparison among individuals with developmental delay/intellectual disability with or without genomic imbalances

BACKGROUND

The chromosomal microarray analysis (CMA) is recommended as a first-tier test for individuals with developmental delay (DD)/intellectual disability (ID) and/or multiple congenital anomalies. However, owing to high costs, this technique is not widely performed for diagnostic purposes in several countries. The aim of this study was to identify clinical features that could favour the hypothesis of genomic imbalances (GIs) in individuals with DD/ID.

METHODS

The sample consisted of 63 individuals, and all of them underwent a detailed evaluation by a clinical geneticist and were investigated by the CMA. They were divided into two groups. Group A composed of 20 individuals with pathogenic copy number variants (CNVs); and group B composed of 43 individuals with normal CMA results or variants of uncertain clinical significance (VUS).

RESULTS

Pathogenic GIs were found in 20 cases (32%), including 11 individuals with an abnormal karyotype, VUS was found in five individuals (8%) and the results were normal in 38 individuals (60%). Major anomalies were found in 15/20 (75%) individuals in group A against 35/43 (81%) in group B. Dysmorphisms (≥5) were found in 17/20 (85%) in group A and 41/43 (95%) in group B. The most frequent major anomalies detected in group A were congenital heart disease, epilepsy and renal malformation; and in group B, they were malformations of central nervous system, congenital heart disease, microcephaly, epilepsy and hearing impairment. There was no significant statistical difference among the frequencies in groups A and B.

CONCLUSIONS

Evidences point that every individual with DD/ID, with no specific clinical suspicion, should have screening for GIs as a first-tier test, regardless of the presence or absence of additional major anomalies or dysmorphisms. Future studies with a similar design would be helpful, especially in countries where the access to new technologies is still limited.