Molecular genetics, neuroimaging outcomes, and structural analyses of novel and recurrent variants of WDR62 gene in two consanguineous Pakistani families with autosomal recessive primary microcephaly.

BACKGROUND: Autosomal recessive primary microcephaly (MCPH) is a rare neurodevelopmental and genetically heterogeneous disorder, characterized by small cranium size (> - 3 SD below mean) and often results in varying degree of intellectual disability. Thirty genes have been identified for the etiology of this disorder due to its clinical and genetic heterogeneity. METHODS AND RESULTS: Here, we report two consanguineous Pakistani families affected with MCPH exhibiting mutation in WDR62 gene. The investigation approach involved Next Generation Sequencing (NGS) gene panel sequencing coupled with linkage analysis followed by validation of identified variants through automated Sanger sequencing and Barcode-Tagged (BT) sequencing. The molecular genetic analysis revealed one novel splice site variant (NM_001083961.2(WDR62):c.1372-1del) in Family A and one known exonic variant NM_001083961.2(WDR62):c.3936dup (p.Val1313Argfs*18) in Family B. Magnetic Resonance Imaging (MRI) scans were also employed to gain insights into the structural architecture of affected individuals. Neurological assessments showed the reduced gyral and sulcal patterns along with normal corpus callosum in affected individuals harboring novel variant. In silico assessments of the identified variants were conducted using different tools to confirm the pathogenicity of these variants. Through In silico analyses, both variants were identified as disease causing and protein modeling of exonic variant indicates subtle conformational alterations in prophesied protein structure. CONCLUSION: This study identifies a novel variant (c.1372-1del) and a recurrent pathogenic variant c.3936dup (p.Val1313Argfs*18) in the WDR62 gene among the Pakistani population, expanding the mutation spectrum for MCPH. These findings emphasize the importance of genetic counseling and awareness to reduce consanguinity and address the burden of this disorder.

WDR62 is involved in spindle assembly by interacting with CEP170 in spermatogenesis.

WDR62 is the second most common genetic alteration associated with microcephaly. It has been shown that Wdr62 is required for germ cell meiosis initiation in mice, and the majority of male germ cells are lost in the meiotic defect of first wave spermatogenesis in Wdr62 mutants. Strikingly, in this study, we found that the initiation of meiosis following spermatogenesis was not affected and the germ cells were gradually repopulated at later developmental stages. However, most germ cells were arrested at metaphase of meiosis I and no mature sperm were detected in epididymides. Further, this study demonstrated that metaphase I arrest of Wdr62-deficient spermatocytes was caused by asymmetric distribution of the centrosome and aberrant spindle assembly. Also, mechanistic studies demonstrated that WDR62 interacts with centrosome-associated protein CEP170, and deletion of Wdr62 causes downregulation of the CEP170 protein, which in turn leads to the aberrant spindle assembly. In summary, this study indicates that the meiosis of first wave spermatogenesis and the following spermatogenesis started from spermatogonium is probably regulated by different mechanisms. We also demonstrated a new function of WDR62 in germ cell meiosis, through its interaction with CEP170.

WDR62 is a novel participator in spindle migration and asymmetric cytokinesis during mouse oocyte meiotic maturation.

In female meiosis, oocyte meiotic maturation is a form of asymmetric cell division, producing the first polar body and a large oocyte, in which the asymmetry of oocyte meiotic division depends on spindle migration and positioning, and cortical polarization. In this study, we conclude that WDR62 (WD40-repeat protein 62) plays an important role in asymmetric meiotic division during mouse oocyte maturation. Our initial study demonstrated that WDR62 mainly co-localized with chromosomes during mouse oocyte meiotic maturation. Interference of Wdr62 by siRNA microinjection did not affect germinal vesicle breakdown (GVBD) but compromised the first polar body extrusion (PBE) with the large polar bodies generated, which is coupled with a higher incidence of spindle abnormality and chromosome misalignment. Further analysis concluded that loss of WDR62 blocked asymmetric spindle positioning and actin cap formation, which should be responsible for large polar body extrusion. Moreover, WDR62 decline intervened with the Arp2/3 complex, an upstream regulator for the cortical actin. Besides for p-MAPK, a critical regulator for the asymmetric division of oocyte, WDR62-depleted oocytes showed perturbation only in localization pattern but not expression level. In summary, our study defines WDR62 as an essential cytoskeletal regulator of spindle migration and asymmetric division during mouse oocyte meiotic maturation.

Novel nephronophthisis-associated variants reveal functional importance of MAPKBP1 dimerization for centriolar recruitment.

Biallelic mutations in MAPKBP1 were recently associated with late-onset cilia-independent nephronophthisis. MAPKBP1 was found at mitotic spindle poles but could not be detected at primary cilia or centrosomes. Here, by identification and characterization of novel MAPKBP1 variants, we aimed at further investigating its role in health and disease. Genetic analysis was done by exome sequencing, homozygosity mapping, and a targeted kidney gene panel while coimmunoprecipitation was used to explore wild-type and mutant protein-protein interactions. Expression of MAPKBP1 in non-ciliated HeLa and ciliated inner medullary collecting duct cells enabled co-localization studies by fluorescence microscopy. By next generation sequencing, we identified two novel homozygous MAPKBP1 splice-site variants in patients with nephronophthisis-related chronic kidney disease. Splice-site analyses revealed truncation of C-terminal coiled-coil domains and patient-derived deletion constructs lost their ability to homodimerize and heterodimerize with paralogous WDR62. While wild-type MAPKBP1 exhibited centrosomal, basal body, and microtubule association, mutant proteins lost the latter and showed reduced recruitment to cell cycle dependent centriolar structures. Wild-type and mutant proteins had no reciprocal influence upon co-expression excluding dominant negative effects. Thus, MAPKBP1 appears to be a novel microtubule-binding protein with cell cycle dependent centriolar localization. Truncation of its coiled-coil domain is enough to abrogate its dimerization and results in severely disturbed intracellular localizations. Delineating the impact of impaired dimerization on cell cycle regulation and intracellular kidney signaling may provide new insights into common mechanisms of kidney degeneration. Thus, due to milder clinical presentation, MAPKBP1-associated nephronophthisis should be considered in adult patients with otherwise unexplained chronic kidney disease.

Mutations in MAPKBP1 Cause Juvenile or Late-Onset Cilia-Independent Nephronophthisis.

Nephronophthisis (NPH), an autosomal-recessive tubulointerstitial nephritis, is the most common cause of hereditary end-stage renal disease in the first three decades of life. Since most NPH gene products (NPHP) function at the primary cilium, NPH is classified as a ciliopathy. We identified mutations in a candidate gene in eight individuals from five families presenting late-onset NPH with massive renal fibrosis. This gene encodes MAPKBP1, a poorly characterized scaffolding protein for JNK signaling. Immunofluorescence analyses showed that MAPKBP1 is not present at the primary cilium and that fibroblasts from affected individuals did not display ciliogenesis defects, indicating that MAPKBP1 may represent a new family of NPHP not involved in cilia-associated functions. Instead, MAPKBP1 is recruited to mitotic spindle poles (MSPs) during the early phases of mitosis where it colocalizes with its paralog WDR62, which plays a key role at MSP. Detected mutations compromise recruitment of MAPKBP1 to the MSP and/or its interaction with JNK2 or WDR62. Additionally, we show increased DNA damage response signaling in fibroblasts from affected individuals and upon knockdown of Mapkbp1 in murine cell lines, a phenotype previously associated with NPH. In conclusion, we identified mutations in MAPKBP1 as a genetic cause of juvenile or late-onset and cilia-independent NPH.

Novel compound heterozygous mutations in WDR62 gene leading to developmental delay and Primary Microcephaly in Saudi Family.

OBJECTIVE: Primary microcephaly (MCPH) is a rare autosomal recessive disorder characterized by impaired congenital reduction of brain size along with head circumference and intellectual disability. MCPH is a heterogeneous disorder and more than twenty four genes associated with this disease have been identified so far. The objective of this study was to find out the novel genes or mutations leading to the genetic defect in a Saudi family with primary microcephaly. METHODS: Whole exome sequencing was carried out to find the novel mutation and the results was further validated using Sanger sequencing analysis. This study was done in the Center of excellence in Genomic Medicine and Research, King Abdulaziz University under KACST project during 2017 and 2018. RESULTS: We report a novel compound heterozygous mutations c.797C>T in exon 7 and c.1102G>A in exon 9 of the WD repeat domain 62 (WDR62) (OMIM 604317) gene in two affected siblings in Saudi family with intellectual disability, speech impediments walking difficulty along with primary microcephaly. Two rare, missense variants were detected in heterozygous state in the WDR62 gene in these two affected individuals from the heterozygous parents. CONCLUSIONS: A compound heterozygous mutations c.797C>T in exon 7 and c.1102G> A in exon 9 of the WDR62 gene was identified. WDR62 gene is very important gene and mutation can lead to neuro developmental defects, brain malformations, reduced brain and head size. These results should be taken into consideration during prognostic discussions and mutation spectrum with affected patients and their families in the Saudi population.

A novel non sense mutation in WDR62 causes autosomal recessive primary microcephaly: a case report.

BACKGROUND: Autosomal recessive primary microcephaly (MCPH) is a rare genetically heterogeneous disorder of neurogenic brain development characterized by a reduced head circumference at birth with no remarkable anomalies of brain architecture and variable degrees of intellectual impairment. Clinical and genetic heterogeneity in genetic disorders represent a major diagnostic challenge. CASE PRESENTATION: Two patients, 11 and 9 years old, born from consanguineous parents, were referred to the department of medical genetics at the National Institute of Health in Rabat. The diagnosis of MCPH was made, based on reduced head circumference without brain architecture abnormalities. The two patients were subject to the whole-exome sequencing, which allowed to diagnose a novel homozygous mutation c.1027C > T; p.Gln343* in exon 8 of WDR62, a gene already known to be related to MCPH. Sanger sequencing confirmed the segregation of the mutation in the family. CONCLUSION: Our data expends the spectrum of mutations in WDR62 gene, proves the efficiency and cost-effectiveness of whole exome sequencing for the molecular diagnosis of genetically heterogeneous disorders such MCPH. Exome sequencing led to the rapid and cost-effective identification of a novel homozygous mutation in WDR62 gene, thereby facilitating genetic counseling.

A Novel c-Jun N-terminal Kinase (JNK) Signaling Complex Involved in Neuronal Migration during Brain Development.

Disturbance of neuronal migration may cause various neurological disorders. Both the transforming growth factor-ß (TGF-ß) signaling and microcephaly-associated protein WDR62 are important for neuronal migration during brain development; however, the underlying molecular mechanisms involved remain unclear. We show here that knock-out or knockdown of Tak1 (TGFß-activated kinase 1) and Jnk2 (c-Jun N-terminal kinase 2) perturbs neuronal migration during cortical development and that the migration defects incurred by knock-out and/or knockdown of Tßr2 (type II TGF-ß receptor) or Tak1 can be partially rescued by expression of TAK1 and JNK2, respectively. Furthermore, TAK1 forms a protein complex with RAC1 and two scaffold proteins of the JNK pathway, the microcephaly-associated protein WDR62 and the RAC1-interacting protein POSH (plenty of Src homology). Components of the complex coordinate with each other in the regulation of TAK1 as well as JNK activities. We suggest that unique JNK protein complexes are involved in the diversified biological and pathological functions during brain development and pathogenesis of diseases.

WDR62 overexpression is associated with a poor prognosis in patients with lung adenocarcinoma.

Human WDR62, which is localized in the cytoplasm including the centrosome, is known to be responsible for primary microcephaly; however, the role of WDR62 abnormality in cancers remains largely unknown. In this study, we aimed to reveal the pathological role of WDR62 abnormality in lung adenocarcinoma (LAC). We first examined the WDR62 mRNA expression level of LAC (n = 64) using a QRT-PCR analysis and found that WDR62 mRNA transcripts were significantly overexpressed in LAC (P = 0.0432, Wilcoxon matched pairs test). An immunohistochemical analysis for LAC (n = 237) showed that WDR62 proteins were also significantly overexpressed in LAC (P < 0.0001, Mann-Whitney U test). A Kaplan-Meier analysis demonstrated that patients with LAC who exhibit WDR62 overexpression have a short overall survival (P = 0.0378, log-rank test), and a multivariate analysis revealed that WDR62 overexpression was an independent predictor of a poor survival outcome among LAC patients (hazard ratio, 2.032; 95% confidence interval, 1.071-3.777; P = 0.0305). Next, we examined the functional effect of WDR62 overexpression on the lung cancer cell line H1299. WDR62-overexpressing lung cancer cells exhibited an increase in cell growth. Moreover, the concurrent overexpression of WDR62 and TPX2, a WDR62-interacting protein that is also overexpressed in LAC, induced centrosome amplification in the lung cells. Finally, we disclosed that the concurrent overexpression of WDR62 and TPX2 is common in diverse human cancers, using data from the Cancer Genome Atlas. These results suggested that WDR62 overexpression is associated with a poor prognosis in patients with LAC and leads to an increase in the malignant potential of lung cells.

Genetic heterogeneity in Pakistani microcephaly families revisited.

Autosomal recessive primary microcephaly (MCPH) is a rare and heterogeneous genetic disorder characterized by reduced head circumference, low cognitive prowess and, in general, architecturally normal brains. As many as 14 different loci have already been mapped. We recruited 35 MCPH families in Pakistan and could identify the genetic cause of the disease in 31 of them. Using homozygosity mapping complemented with whole-exome, gene panel or Sanger sequencing, we identified 12 novel mutations in 3 known MCPH-associated genes - 9 in ASPM, 2 in MCPH1 and 1 in CDK5RAP2. The 2 MCPH1 mutations were homozygous microdeletions of 164,250 and 577,594 bp, respectively, for which we were able to map the exact breakpoints. We also identified four known mutations - three in ASPM and one in WDR62. The latter was initially deemed to be a missense mutation but we demonstrate here that it affects splicing. As to ASPM, as many as 17 out of 27 MCPH5 families that we ascertained in our sample were found to carry the previously reported founder mutation p.Trp1326*. This study adds to the mutational spectra of four known MCPH-associated genes and updates our knowledge about the genetic heterogeneity of MCPH in the Pakistani population considering its ethnic diversity.

Variants in CUL4B are associated with cerebral malformations.

Variants in cullin 4B (CUL4B) are a known cause of syndromic X-linked intellectual disability. Here, we describe an additional 25 patients from 11 families with variants in CUL4B. We identified nine different novel variants in these families and confirmed the pathogenicity of all nontruncating variants. Neuroimaging data, available for 15 patients, showed the presence of cerebral malformations in ten patients. The cerebral anomalies comprised malformations of cortical development (MCD), ventriculomegaly, and diminished white matter volume. The phenotypic heterogeneity of the cerebral malformations might result from the involvement of CUL-4B in various cellular pathways essential for normal brain development. Accordingly, we show that CUL-4B interacts with WDR62, a protein in which variants were previously identified in patients with microcephaly and a wide range of MCD. This interaction might contribute to the development of cerebral malformations in patients with variants in CUL4B.

Severe presentation of WDR62 mutation: is there a role for modifying genetic factors?

Mutations in WDR62 are associated with primary microcephaly; however, they have been reported with wide phenotypic variability. We report on six individuals with novel WDR62 mutations who illustrate this variability and describe three in greater detail. Of the three, one lacks neuromotor development and has severe pachygyria on MRI, another has only delayed speech and motor development and moderate polymicrogyria, and the third has an intermediate phenotype. We observed a rare copy number change of unknown significance, a 17q25qter duplication, in the first severely affected individual. The 17q25 duplication included an interesting candidate gene, tubulin cofactor D (TBCD), crucial in microtubule assembly and disassembly. Sequencing of the non-duplicated allele showed a TBCD missense mutation, predicted to cause a deleterious p.Phe1121Val substitution. Sequencing of a cohort of five patients with WDR62 mutations, including one with an identical mutation and different phenotype, plus 12 individuals with diagnosis of microlissencephaly and another individual with mild intellectual disability (ID) and a 17q25 duplication, did not reveal TBCD mutations. However, immunostaining with tubulin antibodies of cells from patients with both WDR62 and TBCD mutation showed abnormal tubulin network when compared to controls and cells with only the WDR62 mutation. Therefore, we propose that genetic factors contribute to modify the severity of the WDR62 phenotype and, although based on suggestive evidence, TBCD could function as one of such factors.

Autosomal recessive primary microcephaly type 2 associated with a novel WDR62 splicing variant that disrupts the expression of the functional transcript.

Background: Autosomal recessive primary microcephaly (MCPH) is a rare neurodevelopmental disorder characterized primarily by congenital microcephaly and intellectual disability but without extra-central nervous system malformations. This investigation aimed to elucidate the genetic underpinnings of microcephaly in a patient from a Chinese consanguineous family. Methods: A comprehensive clinical assessment, including brain magnetic resonance imaging (MRI), electroencephalogram (EEG), and genetic analyses, was conducted to evaluate the patient's condition. Whole-exome sequencing (WES) was employed to identify the causative gene, followed by Sanger sequencing, to confirm the mutation and its segregation within the family. Reverse transcript polymerase chain reaction (RT-PCR) was utilized to detect changes in splicing. Western blot was employed to reveal the difference of protein expression level between the wild-type and mutant WDR62 in vitro. Results: The patient exhibited classic MCPH symptoms, including microcephaly, recurrent epilepsy, delayed psychomotor development, and intellectual disability. Additionally, asymmetrical limb length was noted as a prominent feature. MRI findings indicated reduced brain volume with cortical malformations, while EEG demonstrated heightened sharp wave activity. A molecular analysis uncovered a novel homozygous variant c.4154-6 C > G in the WDR62 intron, and a functional analysis confirmed the pathogenicity of this mutation, resulting in the formation of an abnormal transcript with premature termination codons. Conclusion: This study enhances our understanding of the genetic heterogeneity associated with MCPH and highlights the pivotal role of genetic testing in the diagnosing and managing of rare neurodevelopmental disorders. Furthermore, it highlights the potential of emerging genetic therapies in treating conditions such as MCPH2.

JNK signaling and its impact on neural cell maturation and differentiation.

C-Jun-N-terminal-kinases (JNKs), members of the mitogen-activated-protein-kinase family, are significantly linked with neurological and neurodegenerative pathologies and cancer progression. However, JNKs serve key roles under physiological conditions, particularly within the central-nervous-system (CNS), where they are critical in governing neural proliferation and differentiation during both embryogenesis and adult stages. These processes control the development of CNS, avoiding neurodevelopment disorders. JNK are key to maintain the proper activity of neural-stem-cells (NSC) and neural-progenitors (NPC) that exist in adults, which keep the convenient brain plasticity and homeostasis. This review underscores how the interaction of JNK with upstream and downstream molecules acts as a regulatory mechanism to manage the self-renewal capacity and differentiation of NSC/NPC during CNS development and in adult neurogenic niches. Evidence suggests that JNK is reliant on non-canonical Wnt components, Fbw7-ubiquitin-ligase, and WDR62-scaffold-protein, regulating substrates such as transcription factors and cytoskeletal proteins. Therefore, understanding which pathways and molecules interact with JNK will bring knowledge on how JNK activation orchestrates neuronal processes that occur in CNS development and brain disorders.

WDR62-deficiency Causes Autism-like Behaviors Independent of Microcephaly in Mice.

Brain size abnormality is correlated with an increased frequency of autism spectrum disorder (ASD) in offspring. Genetic analysis indicates that heterozygous mutations of the WD repeat domain 62 (WDR62) are associated with ASD. However, biological evidence is still lacking. Our study showed that Wdr62 knockout (KO) led to reduced brain size with impaired learning and memory, as well as ASD-like behaviors in mice. Interestingly, Wdr62 Nex-cKO mice (depletion of WDR62 in differentiated neurons) had a largely normal brain size but with aberrant social interactions and repetitive behaviors. WDR62 regulated dendritic spinogenesis and excitatory synaptic transmission in cortical pyramidal neurons. Finally, we revealed that retinoic acid gavages significantly alleviated ASD-like behaviors in mice with WDR62 haploinsufficiency, probably by complementing the expression of ASD and synapse-related genes. Our findings provide a new perspective on the relationship between the microcephaly gene WDR62 and ASD etiology that will benefit clinical diagnosis and intervention of ASD.

Clinical and genetic analyses in syndromic intellectual disability with primary microcephaly reveal biallelic and de novo variants in patients with parental consanguinity.

BACKGROUND: Syndromic intellectual disability (ID) with accompanying primary microcephaly is a group of rare neurodevelopmental disorders exhibiting extreme genetic and clinical heterogeneity. This layered heterogeneity can partially be resolved by unbiased genetic approaches targeting the genome with next generation sequencing (NGS) technologies, including exome sequencing (ES). OBJECTIVE: This study was performed to dissect the clinical and genetic features in five distinct IDM cases. METHODS: Singleton or trio ES approach followed by in-depth variant analysis using alternative inheritance models was performed. RESULTS: We have identified biallelic loss of function variants in genes WDR62 and AP4M1 in three families, together with de novo missense variants in genes SOX11 and TRIO in two families. ES based haplotype analysis in two cases upon identification of an identical WDR62 variant in the homozygous state in two cases was suggestive of a small shared haplotype of 0.1 Mb. Additionally, we have shown a paternal origin for the de novo variant in TRIO via a polymorphic tag SNP, which enlightens the mutational mechanism for this variant. CONCLUSION: In populations with high parental consanguinity, an autosomal recessive inheritance pattern for data analysis is usually the most obvious choice. Therefore, heterozygous variants may be overlooked in standard NGS analyses in consanguineous families. Our findings underlie the importance of using multiple inheritance models in NGS data analysis.

Microcephaly-associated protein WDR62 shuttles from the Golgi apparatus to the spindle poles in human neural progenitors.

WDR62 is a spindle pole-associated scaffold protein with pleiotropic functions. Recessive mutations in WDR62 cause structural brain abnormalities and account for the second most common cause of autosomal recessive primary microcephaly (MCPH), indicating WDR62 as a critical hub for human brain development. Here, we investigated WDR62 function in corticogenesis through the analysis of a C-terminal truncating mutation (D955AfsX112). Using induced Pluripotent Stem Cells (iPSCs) obtained from a patient and his unaffected parent, as well as isogenic corrected lines, we generated 2D and 3D models of human neurodevelopment, including neuroepithelial stem cells, cerebro-cortical progenitors, terminally differentiated neurons, and cerebral organoids. We report that WDR62 localizes to the Golgi apparatus during interphase in cultured cells and human fetal brain tissue, and translocates to the mitotic spindle poles in a microtubule-dependent manner. Moreover, we demonstrate that WDR62 dysfunction impairs mitotic progression and results in alterations of the neurogenic trajectories of iPSC neuroderivatives. In summary, impairment of WDR62 localization and function results in severe neurodevelopmental abnormalities, thus delineating new mechanisms in the etiology of MCPH.

Novel phenotype and genotype spectrum of WDR62 in two patients with associated primary autosomal recessive microcephaly.

BACKGROUND: Microcephaly is a prominent feature of patients with primary autosomal recessive microcephaly 2 (MCPH2) caused by mutations in the WD Repeat Domain 62 (WDR62; OMIM: 613,583). AIM: The study aimed to identify the underlying genetic factor(s) causing microcephaly in two patients in a consanguineous Iranian family. METHODS: Two male patients (11 and 27 years old) were noticed due to microcephaly, neurodevelopmental delay, and occasional seizures. The younger patient (the proband) was subjected to paired-end whole-exome sequencing followed by Sanger sequencing to detect any underlying genetic factor. RESULTS: Upon examination, both patients showed microcephaly as a prominent manifestation; they were under-weighted as well. The patients had a moderate gross motor impairment, severe cognitive disability and speech delay, increased deep tendon reflexes, flexible joint contractures, sensorineural hearing loss, and vertical nystagmus as a new ocular finding. The proband had more severe neurodevelopmental delay symptoms. The brain magnetic resonance imaging series revealed severe structural and cortical brain abnormalities in addition to hemiatrophy. Using Whole-exome Sequencing, a novel homozygous missense variant-NM_001083961.2; c.1598A > G: p.(His533Arg)-was identified in the WDR62. Subsequently, in silico analyses determined the possible impacts of the novel variant on the structure and function of WDR62 protein. CONCLUSIONS: Herein, we identified a novel homozygous missense variant in the WDR62 in two patients with MCPH2. Vertical nystagmus and sensorineural hearing loss were detected as novel neurological findings. The present study expands the phenotype and genotype spectrum of MCPH2.

Autosomal Recessive Primary Microcephaly (MCPH) and Novel Pathogenic Variants in ASPM and WDR62 Genes.

Introduction: Autosomal recessive primary microcephaly (MCPH) is a disorder characterized by congenital microcephaly and intellectual disability without extra-central nervous system malformation. MCPH is a disease with heterogeneity in genotype and phenotype. For this reason, it is important to determine the genetic causes and genotype-phenotype relationship in MCPH, which causes lifelong impairment. In this study, we aimed to evaluate the clinical, genetic, and brain imaging findings of cases diagnosed with MCPH. Methods: Electroencephalogram and brain magnetic resonance imaging were performed for all cases. We evaluated genetic results of the 39 families including cases with suspected MCPH diagnosis. Results: Genetic diagnosis related to MCPH was provided in 11/39 (28.2%) of these families including 13/41 cases (31.7%). Variants of the WDR62 gene were the most common (61.5%) cause, and variants of the ASPM gene were the second most common cause (38.5%). We have found 6 novel variants and 4 previously reported variants in ASPM and WDR62 genes. Main brain imaging findings in our cases were lissencephaly, polymicrogyria, schizencephaly, pachygyria, and cortical dysplasia. Genetic counseling in 2 families whose genetic diagnosis was determined prevented them from having another child with MCPH. Discussion/Conclusion: Detection and reporting of novel variants is an important step in eliminating this disorder by providing families with appropriate genetic counseling.

WD repeat domain 62 (WDR62) promotes resistance of colorectal cancer to oxaliplatin through modulating mitogen-activated protein kinase (MAPK) signaling.

WD repeat domain 62 (WDR62) is involved in embryonic brain growth through regulation of glial and neural cell populations. WDR62 is also implicated in the carcinogenesis of various cancers. The role of WDR62 in progression and chemoresistance of colorectal cancer (CRC) was investigated. Firstly, oxaliplatin-resistant CRC cells (HCT116/R and HT29/R) were sequentially exposed to an increasing concentration of oxaliplatin. The results showed that WDR62 was elevated in CRC tissues, and oxaliplatin resistance conferred up-regulation of WDR62 in CRC cells. Knockdown of WDR62 reduced cell proliferation and promoted the apoptosis of oxaliplatin-resistant CRC cells. Moreover, silencing of WDR62 increased fluorescence intensity of γH2AX, and decreased protein expression of p-DNA-PK and Rad51 in the oxaliplatin-resistant CRC cells. The protein expression of p-ERK, p-JNK, and p-p38 in oxaliplatin-resistant CRC cells were down-regulated by knockdown of WDR62. In conclusion, silencing of WDR62 suppressed oxaliplatin resistance and DNA damage repair of CRC cells through inactivation of MAPK signaling.