Congenital microcephaly‐linked CDK5RAP2 affects eye development

Serum RNA Profile Reflects Fluid Status and Atrophic Retinal Changes in Neovascular Age-Related Macular Degeneration

The increasing prevalence of age-related macular degeneration (AMD), a disease that can result in the loss of central vision, is an emerging problem worldwide due to aging societies. Growing patient numbers create a challenge for the healthcare system. Understanding the mechanisms of AMD pathogenesis will aid in early, personalized, and efficient intervention, helping to mitigate this issue. Current diagnostic methods rely on optical coherence tomography and angiography imaging, which identify existing damages, but do not provide information on the mechanisms behind them. In the present work, we demonstrate a difference in the serum RNA profile between neovascular AMD (nAMD) patients and controls. Moreover, the RNA profile of nAMD patients corresponded with anatomical changes in the retinal fluid compartments as well as atrophic changes of the retina. We followed two independent ways to control false positive leads, and when these approaches were combined, thioredoxin-related transmembrane protein 4 (TMX4) was observed to be differentially expressed by both approaches. This finding opens a new pathway in AMD studies, which are limited due to restricted access to live human target material and the limited value of animal models of human AMD.

Serological proteomic profiling uncovered CDK5RAP2 as a novel marker in benign prostatic hyperplasia

BACKGROUND

Benign prostatic hyperplasia (BPH) affects approximately half of men over the age of 50. Early detection and timely treatment facilitate disease intervention and achieve a better clinical outcome. However, current clinical methods, such as prostate specific antigen (PSA), lack the sensitivity to accurately distinguish between BPH and prostate cancer (PCa). Thus, optimal serum markers are warranted to complement existing diagnostic tests.

METHODS

In this study, we recruited 1987 BPH patients and characterized their clinical features. To explore BPH proteomic alterations, a data independent acquisition-based mass spectrometry proteomics approach was adopted for 66 serum samples from healthy males (n = 22), patients with BPH (n = 22) and prostate cancer (n = 22). Bioinformatic evaluations were performed for proteomic profiling and candidate selection. In addition, a promising candidate was further validated with ELISA assay.

RESULTS

Our findings revealed that the level of free PSA correlated with prostate volume. 7.95 % of BPH patients had a PSA value greater than 10 ng/mL, with elevated free PSA, prostate volume, PSA density, and decreased free to total PSA ratio. Mass spectrometry-based serum profiling demonstrated distinct differences between BPH and PCa. CDK5RAP2 was weighted most important in BPH patients' serum and achieved an area under the receiver operating characteristic curve of 0.900 in distinguishing BPH and PCa, which was further validated by publicly-available mRNA microarray analysis and cellular phenotype evaluation.

CONCLUSION

Our comprehensive analysis systematically explored BPH serum characteristics, proteomic profiles, and identified novel serum markers that may contribute to the understanding of BPH and facilitate early diagnosis and intervention.

Roles of Cep215/Cdk5rap2 in establishing testicular architecture for mouse male germ cell development

Cep215/Cdk5rap2 is a centrosome protein crucial for directing microtubule organization during cell division and morphology. Cep215 is a causal gene of autosomal recessive primary microcephaly type 3, characterized by a small brain size and a thin cerebral cortex. Despite previous attempts with Cep215 knockout (KO) mice to elucidate its developmental roles, interpreting their phenotypes remained challenging due to potential interference from alternative variants. Here, we generated KO mice completely lacking the Cep215 gene and investigated its specific contributions to male germ cell development. In the absence of Cep215, testis size decreased significantly, accompanied by a reduction in male germ cell numbers. Histological analyses unveiled the arrested development of male germ cells around the zygotene stage of meiosis. Concurrently, the formation of the blood-testis barrier (BTB) was impaired in Cep215 KO testes. These findings suggest that BTB failure contributes, at least partially, to male germ cell defects observed in Cep215 KO mice. We propose that the deletion of Cep215 may disrupt microtubule organization in Sertoli cells with a delay in spermatogonial stem cell mitosis, thereby impeding proper BTB formation.

Arl2 GTPase associates with the centrosomal protein Cdk5rap2 to regulate cortical development via microtubule organization

ADP ribosylation factor-like GTPase 2 (Arl2) is crucial for controlling mitochondrial fusion and microtubule assembly in various organisms. Arl2 regulates the asymmetric division of neural stem cells in Drosophila via microtubule growth. However, the function of mammalian Arl2 during cortical development was unknown. Here, we demonstrate that mouse Arl2 plays a new role in corticogenesis via regulating microtubule growth, but not mitochondria functions. Arl2 knockdown (KD) leads to impaired proliferation of neural progenitor cells (NPCs) and neuronal migration. Arl2 KD in mouse NPCs significantly diminishes centrosomal microtubule growth and delocalization of centrosomal proteins Cdk5rap2 and γ-tubulin. Moreover, Arl2 physically associates with Cdk5rap2 by in silico prediction using AlphaFold multimer, which was validated by co-immunoprecipitation and proximity ligation assay. Remarkably, Cdk5rap2 overexpression significantly rescues the neurogenesis defects caused by Arl2 KD. Therefore, Arl2 plays an important role in mouse cortical development through microtubule growth via the centrosomal protein Cdk5rap2.

Proteome changes in autosomal recessive primary microcephaly

BACKGROUND/AIM

Autosomal recessive primary microcephaly (MCPH) is a rare and genetically heterogeneous group of disorders characterized by intellectual disability and microcephaly at birth, classically without further organ involvement. MCPH3 is caused by biallelic variants in the cyclin-dependent kinase 5 regulatory subunit-associated protein 2 gene CDK5RAP2. In the corresponding Cdk5rap2 mutant or Hertwig's anemia mouse model, congenital microcephaly as well as defects in the hematopoietic system, germ cells and eyes have been reported. The reduction in brain volume, particularly affecting gray matter, has been attributed mainly to disturbances in the proliferation and survival of early neuronal progenitors. In addition, defects in dendritic development and synaptogenesis exist that affect the excitation-inhibition balance. Here, we studied proteomic changes in cerebral cortices of Cdk5rap2 mutant mice.

MATERIAL AND METHODS

We used large-gel two-dimensional gel (2-DE) electrophoresis to separate cortical proteins. 2-DE gels were visualized by a trained observer on a light box. Spot changes were considered with respect to presence/absence, quantitative variation and altered mobility.

RESULT

We identified a reduction in more than 30 proteins that play a role in processes such as cell cytoskeleton dynamics, cell cycle progression, ciliary functions and apoptosis. These proteome changes in the MCPH3 model can be associated with various functional and morphological alterations of the developing brain.

CONCLUSION

Our results shed light on potential protein candidates for the disease-associated phenotype reported in MCPH3.

Homozygous mutation in MCM7 causes autosomal recessive primary microcephaly and intellectual disability

Background

Minichromosomal maintenance (MCM) complex components 2, 4, 5 and 6 have been linked to human disease with phenotypes including microcephaly and intellectual disability. The MCM complex has DNA helicase activity and is thereby important for the initiation and elongation of the replication fork and highly expressed in proliferating neural stem cells.

Methods

Whole-exome sequencing was applied to identify the genetic cause underlying the neurodevelopmental disease of the index family. The expression pattern of Mcm7 was characterised by performing quantitative real-time PCR, in situ hybridisation and immunostaining. To prove the disease-causative nature of identified MCM7, a proof-of-principle experiment was performed.

Results

We reported that the homozygous missense variant c.793G>A/p.A265T (g.7:99695841C>T, NM_005916.4) in MCM7 was associated with autosomal recessive primary microcephaly (MCPH), severe intellectual disability and behavioural abnormalities in a consanguineous pedigree with three affected individuals. We found concordance between the spatiotemporal expression pattern of Mcm7 in mice and a proliferative state: Mcm7 expression was higher in early mouse developmental stages and in proliferative zones of the brain. Accordingly, Mcm7/MCM7 levels were detectable particularly in undifferentiated mouse embryonal stem cells and human induced pluripotent stem cells compared with differentiated neurons. We further demonstrate that the downregulation of Mcm7 in mouse neuroblastoma cells reduces cell viability and proliferation, and, as a proof-of-concept, that this is counterbalanced by the overexpression of wild-type but not mutant MCM7.

Conclusion

We report mutations of MCM7 as a novel cause of autosomal recessive MCPH and intellectual disability and highlight the crucial function of MCM7 in nervous system development.