Variants in 46,XY DSD-Related Genes in Syndromic and Non-Syndromic Small for Gestational Age Children with Hypospadias

Hypospadias is a common congenital disorder of male genital formation. Children born small for gestational age (SGA) present a high frequency of hypospadias of undetermined etiology. No previous study investigated the molecular etiology of hypospadias in boys born SGA using massively parallel sequencing. Our objective is to report the genetic findings of a cohort of patients born SGA with medium or proximal hypospadias. We identified 46 individuals with this phenotype from a large cohort of 46,XY DSD patients, including 5 individuals with syndromic features. DNA samples from subjects were studied by either whole exome sequencing or target gene panel approach. Three of the syndromic patients have 5 main clinical features of Silver-Russell syndrome (SRS) and were first studied by MLPA. Among the syndromic patients, loss of DNA methylation at the imprinting control region <i>H19/IGF2</i> was identified in 2 individuals with SRS clinical diagnosis. Two novel pathogenic variants in compound heterozygous state were identified in the <i>CUL7</i> gene establishing the diagnosis of 3M syndrome in one patient, and a novel homozygous variant in <i>TRIM37</i> was identified in another boy with Mulibrey nanism phenotype. Among the non-syndromic subjects, 7 rare heterozygous variants were identified in 6 DSD-related genes. However, none of the variants found can explain the phenotype by themselves. In conclusion, a genetic defect that clarifies the etiology of hypospadias was not found in most of the non-syndromic SGA children, supporting the hypothesis that multifactorial causes, new genes, and/or unidentified epigenetic defects may have an influence in this condition.

TRIM37 prevents formation of condensate-organized ectopic spindle poles to ensure mitotic fidelity

Centrosomes are composed of a centriolar core surrounded by pericentriolar material that nucleates microtubules. The ubiquitin ligase TRIM37 localizes to centrosomes, but its centrosomal roles are not yet defined. We show that TRIM37 does not control centriole duplication, structure, or the ability of centrioles to form cilia but instead prevents assembly of an ectopic centrobin-scaffolded structured condensate that forms by budding off of centrosomes. In ∼25% of TRIM37-deficient cells, the condensate organizes an ectopic spindle pole, recruiting other centrosomal proteins and acquiring microtubule nucleation capacity during mitotic entry. Ectopic spindle pole–associated transient multipolarity and multipolar segregation in TRIM37-deficient cells are suppressed by removing centrobin, which interacts with and is ubiquitinated by TRIM37. Thus, TRIM37 ensures accurate chromosome segregation by preventing the formation of centrobin-scaffolded condensates that organize ectopic spindle poles. Mutations in TRIM37 cause the disorder mulibrey nanism, and patient-derived cells harbor centrobin condensate-organized ectopic poles, leading us to propose that chromosome missegregation is a pathological mechanism in this disorder.

TRIM37 prevents formation of centriolar protein assemblies by regulating Centrobin

TRIM37 is an E3 ubiquitin ligase mutated in Mulibrey nanism, a disease with impaired organ growth and increased tumor formation. TRIM37 depletion from tissue culture cells results in supernumerary foci bearing the centriolar protein Centrin. Here, we characterize these centriolar protein assemblies (Cenpas) to uncover the mechanism of action of TRIM37. We find that an atypical de novo assembly pathway can generate Cenpas that act as microtubule-organizing centers (MTOCs), including in Mulibrey patient cells. Correlative light electron microscopy reveals that Cenpas are centriole-related or electron-dense structures with stripes. TRIM37 regulates the stability and solubility of Centrobin, which accumulates in elongated entities resembling the striped electron dense structures upon TRIM37 depletion. Furthermore, Cenpas formation upon TRIM37 depletion requires PLK4, as well as two parallel pathways relying respectively on Centrobin and PLK1. Overall, our work uncovers how TRIM37 prevents Cenpas formation, which would otherwise threaten genome integrity.

TRIM37 prevents formation of centriolar protein assemblies by regulating Centrobin stability

ABSTRACTTRIM37 is an E3 ubiquitin ligase mutated in Mulibrey nanism, a disease characterized by impaired growth and increased tumorigenesis, whose cellular etiology is poorly understood. TRIM37 depletion from tissue culture cells results in supernumerary foci bearing the centriolar protein Centrin. Here, we characterized these centriolar protein assemblies (Cenpas) to uncover the mechanism of action of TRIM37. We established that an atypical de novo assembly pathway is notably involved in forming Cenpas, which can nevertheless trigger further centriole assembly and act as MTOCs. We found also that Cenpas are present and act similarly in Mulibrey patient cells. Through correlative light electron microscopy, we uncovered that Cenpas correspond to centriole related structures and elongated electron-dense structures with stripes. Importantly, we established that TRIM37 regulates the stability and solubility of the centriolar protein Centrobin. Our findings suggest that elongated Centrobin assemblies are a major constituent of the striped electron dense structures. Furthermore, we established that Cenpas formation upon TRIM37 depletion requires PLK4 activity, as well as two parallel pathways relying respectively on Centrobin and PLK1. Overall, our work uncovers how TRIM37 prevents the formation of Cenpas that would otherwise threaten genome integrity, including possibly in Mulibrey patients.