JADE1 is dispensable for the brain development in mice.

In mammalian brain development, WNT signaling balances proliferation and differentiation of neural progenitor cells, and is essential for the maintenance of regular brain development. JADE1 is a candidate transcription co-factor essential for DNA replication, cell division, and cell cycle regulation. In 293T cells, JADE1 is stabilized by von Hippel-Lindau protein pVHL, promotes the ß-catenin ubiquitination and thus blunts canonical WNT signaling. Furthermore, JADE1 inhibits ß-catenin-induced ectopic axis formation in Xenopus embryos. However, JADE1's role in mammalian brain development remains unknown. Here, we generated a new Jade1 knockout mouse line using CRISPR-Cas9 technology. We found that JADE1 null resulted in decreased survival rate, reduced body weight and brain weight in mice. However, histological analysis revealed a normal brain development. Furthermore, Jade1 null neural progenitor cells proliferated normally in vivo and in vitro. RNA-seq analysis further showed that JADE1 loss did not affect the cerebral cortex gene expression. Our findings indicate that JADE1 is dispensable for developing the cerebral cortex in mice.

Ezh2 promotes clock function and hematopoiesis independent of histone methyltransferase activity in zebrafish.

EZH2 is a subunit of polycomb repressive complex 2 (PRC2) that silences gene transcription via H3K27me3 and was shown to be essential for mammalian liver circadian regulation and hematopoiesis through gene silencing. Much less, however, is known about how Ezh2 acts in live zebrafish. Here, we show that zebrafish ezh2 is regulated directly by the circadian clock via both E-box and RORE motif, while core circadian clock genes per1a, per1b, cry1aa and cry1ab are down-regulated in ezh2 null mutant and ezh2 morphant zebrafish, and either knockdown or overexpression of ezh2 alters locomotor rhythms, indicating that Ezh2 is required for zebrafish circadian regulation. In contrast to its canonical silencing function, zebrafish Ezh2 up-regulates these key circadian clock genes independent of histone methyltransferase activity by directly binding to key circadian clock proteins. Similarly, Ezh2 contributes to hematopoiesis by enhancing expression of hematopoietic genes such as cmyb and lck. Together, our findings demonstrate for the first time that Ezh2 acts in both circadian regulation and hematopoiesis independent of silencing PRC2.

UPF3A is dispensable for nonsense-mediated mRNA decay in mouse pluripotent and somatic cells.

Nonsense-mediated mRNA decay (NMD) is a highly conserved regulatory mechanism of post-transcriptional gene expression in eukaryotic cells. NMD plays essential roles in mRNA quality and quantity control and thus safeguards multiple biological processes including embryonic stem cell differentiation and organogenesis. UPF3A and UPF3B in vertebrate species, originated from a single UPF3 gene in yeast, are key factors in the NMD machinery. Although UPF3B is a well-recognized weak NMD-promoting factor, whether UPF3A functions in promoting or suppressing NMD is under debate. In this study, we generated a Upf3a conditional knockout mouse strain and established multiple lines of embryonic stem cells and somatic cells without UPF3A. Through extensive analysis on the expressions of 33 NMD targets, we found UPF3A neither represses NMD in mouse embryonic stem cells, somatic cells, nor in major organs including the liver, spleen, and thymus. Our study reinforces that UPF3A is dispensable for NMD when UPF3B is present. Furthermore, UPF3A may weakly and selectively promote NMD in certain murine organs.

The Central Domain of MCPH1 Controls Development of the Cerebral Cortex and Gonads in Mice.

MCPH1 is the first gene identified to be responsible for the human autosomal recessive disorder primary microcephaly (MCPH). Mutations in the N-terminal and central domains of MCPH1 are strongly associated with microcephaly in human patients. A recent study showed that the central domain of MCPH1, which is mainly encoded by exon 8, interacts with E3 ligase ßTrCP2 and regulates the G2/M transition of the cell cycle. In order to investigate the biological functions of MCPH1's central domain, we constructed a mouse model that lacked the central domain of MCPH1 by deleting its exon 8 (designated as Mcph1-Δe8). Mcph1-Δe8 mice exhibited a reduced brain size and thinner cortex, likely caused by a compromised self-renewal capacity and premature differentiation of Mcph1-Δe8 neuroprogenitors during corticogenesis. Furthermore, Mcph1-Δe8 mice were sterile because of a loss of germ cells in the testis and ovary. The embryonic fibroblasts of Mcph1-Δe8 mice exhibited premature chromosome condensation (PCC). All of these findings indicate that Mcph1-Δe8 mice are reminiscent of MCPH1 complete knockout mice and Mcph1-ΔBR1 mice. Our study demonstrates that the central domain of MCPH1 represses microcephaly, and is essential for gonad development in mammals.

Spatial expression of the nonsense-mediated mRNA decay factors UPF3A and UPF3B among mouse tissues / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

无义介导的信使RNA（mRNA）降解途径（nonsense-mediated mRNA decay，简称为NMD)是真核生物细胞内一种重要的基因转录后表达调控机制，它积极参与一系列细胞生理和生化过程，控制细胞命运和生命体的组织稳态。NMD的缺陷会导致人类疾病，如神经发育障碍、肿瘤发生和自身免疫疾病等。UPF3 (Up-frameshift protein 3)是一个核心的NMD因子，它最早在酵母中被发现。UPF3A和UPF3B是UPF3在生物进化到脊椎动物阶段出现的两个旁系同源物，在NMD中具有激活或抑制的作用。以往研究发现，UPF3B蛋白几乎在所有哺乳动物器官中均有表达，而UPF3A蛋白在除睾丸外的大多数哺乳动物组织中难以被检测到。解释这一现象的假说为：在NMD途径中，UPF3B具有比UPF3A更高的竞争性结合UPF2的能力，UPF3B和UPF2的结合促使UPF3A成为游离状态，而游离的UPF3A蛋白不稳定且易被降解。此假说提示UPF3A和UPF3B在NMD中存在拮抗作用。在本研究中，我们重新定量评估了UPF3A和UPF3B在野生型成年雄性和雌性小鼠的9个主要组织和生殖器官中的mRNA和蛋白表达，结果证实UPF3A在雄性生殖细胞中表达量最高。令人惊讶的是，我们发现在包括大脑和胸腺在内的大多数组织中，UPF3A与UPF3B的蛋白水平相当，而在小鼠脾、肺组织中，UPF3A表达高于UPF3B。公共基因表达数据进一步支持了上述发现。因此，我们的研究表明了UPF3A是小鼠组织中普遍表达的NMD因子。同时，该研究结果推测：在生理条件下，UPF3A和UPF3B蛋白之间不存在竞争抑制，且UPF3A在多种哺乳动物组织的稳态中发挥重要作用。