[Analysis of a child with neurodevelopmental disorders due to variant of HNRNPU gene and a literature review].

OBJECTIVE: To explore the clinical characteristics and genetic variant in a child with neurodevelopmental disorders (NDDs). METHODS: Clinical data of a child who had presented at Xiaogan Hospital Affiliated to Wuhan University of Science and Technology in December 2020 due to intermittent convulsions for over a year were retrospectively analyzed. Peripheral blood samples of the child and his parents were collected and subjected to whole exome sequencing. Candidate variants were verified by Sanger sequencing and bioinformatic analysis. "HNRNPU gene", "epilepsy", "epileptic encephalopathy", "hereditary epilepsy", "neurodevelopmental disorder", "neurodevelopmental syndrome", "HNRNPU", and "NDDs" were used as the key words to search the CNKI, Wanfang and PubMed databases dated from January 1, 1994 to February 10, 2022. RESULTS: The patient was a 2-year-old boy who had developed seizure at the age of 5 months. His clinical features had included abnormal appearance, recurrent seizures, and low developmental quotients of each functional area as evaluated by the Gesell scale. The child was given sodium valproate for the antiepileptic treatment and rehabilitation training. He had become seizure-free within half a year of follow-up, but his intelligence and motor development did not improve significantly. Genetic testing revealed that he has harbored a heterozygous c.1720_1722delCTT (p.Lys574del) variant of the HNRNPU gene, which was not found in either of his parents. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was rated as likely pathogenic (PS2+PM2_Supporting+PM4). A total of 13 articles were retrieved, and the types of HNRNPU gene mutations have included splice site mutation, nonsense mutation, missense mutation, in-frame deletion, gene duplication, frameshifting mutation, and multiple exon deletion. The main clinical manifestations have included mental retardation, language delay, global developmental delay, epilepsy, craniofacial deformity, mental and behavioral abnormalities. CONCLUSION: The c.1720_1722delCTT variant of the HNRNPU gene probably underlay the NDDs in this child. Above finding has enriched the mutational spectrum of the HNRNPU gene.

MUC1 triggers lineage plasticity of Her2 positive mammary tumors.

Aberrant overexpression of mucin 1 (MUC1) and human epidermal growth factor receptor 2 (HER2) are often observed in breast cancer. However, the role of concomitant MUC1/HER2 in the development of breast cancer has not been fully illustrated. Following analysis of public microarray datasets that revealed a correlation between double MUC1 and HER2 positivity and a worse clinical outcome, we generated a mouse model overexpressing both Her2 and MUC1 cytoplasmic domain (MUC1-CD) to investigate their interaction in mammary carcinogenesis. Coexpression of Her2 and MUC1-CD conferred a growth advantage and promoted the development of spontaneous mammary tumors. Genomic analysis revealed that enforced expression of MUC1-CD and Her2 induces mammary tumor lineage plasticity, which is supported by gene reprogramming and mammary stem cell enrichment. Through gain- and loss-of-function strategies, we show that coexpression of Her2 and MUC1-CD is associated with downregulation of tricarboxylic acid (TCA) cycle genes in tumors. Importantly, the reduction in TCA cycle genes induced by MUC1-CD was found to be significantly connected to poor prognosis in HER2+ breast cancer patients. In addition, MUC1 augments the Her2 signaling pathway by inducing Her2/Egfr dimerization. These findings collectively demonstrate the vital role of MUC1-CD/Her2 collaboration in shaping the mammary tumor landscape and highlight the prognostic and therapeutic implications of MUC1 in patients with HER2+ breast cancer.

Matrix softness regulates plasticity of tumour-repopulating cells via H3K9 demethylation and Sox2 expression.

Tumour-repopulating cells (TRCs) are a self-renewing, tumorigenic subpopulation of cancer cells critical in cancer progression. However, the underlying mechanisms of how TRCs maintain their self-renewing capability remain elusive. Here we show that relatively undifferentiated melanoma TRCs exhibit plasticity in Cdc42-mediated mechanical stiffening, histone 3 lysine residue 9 (H3K9) methylation, Sox2 expression and self-renewal capability. In contrast to differentiated melanoma cells, TRCs have a low level of H3K9 methylation that is unresponsive to matrix stiffness or applied forces. Silencing H3K9 methyltransferase G9a or SUV39h1 elevates the self-renewal capability of differentiated melanoma cells in a Sox2-dependent manner. Mechanistically, H3K9 methylation at the Sox2 promoter region inhibits Sox2 expression that is essential in maintaining self-renewal and tumorigenicity of TRCs both in vitro and in vivo. Taken together, our data suggest that 3D soft-fibrin-matrix-mediated cell softening, H3K9 demethylation and Sox2 gene expression are essential in regulating TRC self-renewal.

Generation of organized germ layers from a single mouse embryonic stem cell.

Mammalian inner cell mass cells undergo lineage-specific differentiation into germ layers of endoderm, mesoderm and ectoderm during gastrulation. It has been a long-standing challenge in developmental biology to replicate these organized germ layer patterns in culture. Here we present a method of generating organized germ layers from a single mouse embryonic stem cell cultured in a soft fibrin matrix. Spatial organization of germ layers is regulated by cortical tension of the colony, matrix dimensionality and softness, and cell-cell adhesion. Remarkably, anchorage of the embryoid colony from the 3D matrix to collagen-1-coated 2D substrates of ~1 kPa results in self-organization of all three germ layers: ectoderm on the outside layer, mesoderm in the middle and endoderm at the centre of the colony, reminiscent of generalized gastrulating chordate embryos. These results suggest that mechanical forces via cell-matrix and cell-cell interactions are crucial in spatial organization of germ layers during mammalian gastrulation. This new in vitro method could be used to gain insights on the mechanisms responsible for the regulation of germ layer formation.

The cytoplasmic domain of MUC1 induces hyperplasia in the mammary gland and correlates with nuclear accumulation of ß-catenin.

MUC1 is an oncoprotein that is overexpressed in up to 90% of breast carcinomas. A previous in vitro study by our group demonstrated that the cytoplasmic domain of MUC1 (MUC1-CD), the minimal functional unit of MUC1, contributes to the malignant phenotype in cells by binding directly to ß-catenin and protecting ß-catenin from GSK3ß-induced degradation. To understand the in vivo role of MUC1-CD in breast development, we generated a MUC1-CD transgenic mouse model under the control of the MMTV promoter in a C57BL/6J background, which is more resistant to breast tumor. We show that the expression of MUC1-CD in luminal epithelial cells of the mammary gland induced a hyperplasia phenotype characterized by the development of hyper-branching and extensive lobuloalveoli in transgenic mice. In addition to this hyperplasia, there was a marked increase in cellular proliferation in the mouse mammary gland. We further show that MUC1-CD induces nuclear localization of ß-catenin, which is associated with a significant increase of ß-catenin activity, as shown by the elevated expression of cyclin D1 and c-Myc in MMTV-MUC1-CD mice. Consistent with this finding, we observed that overexpression of MUC1-C is associated with ß-catenin nuclear localization in tumor tissues and increased expression of Cyclin D1 and c-Myc in breast carcinoma specimens. Collectively, our data indicate a critical role for MUC1-CD in the development of mammary gland preneoplasia and tumorigenesis, suggesting MUC1-CD as a potential target for the diagnosis and chemoprevention of human breast cancer.