Prior to the pairing and recombination between homologous chromosomes during meiosis, telomeres attach to the nuclear envelope and form a transient cluster. However, the protein factors mediating meiotic telomere attachment to the nuclear envelope and the requirement of this attachment for homolog pairing and synapsis have not been determined in animals. Here we show that the inner nuclear membrane protein SUN1 specifically associates with telomeres between the leptotene and diplotene stages during meiotic prophase I. Disruption of Sun1 in mice prevents telomere attachment to the nuclear envelope, efficient homolog pairing, and synapsis formation in meiosis. Massive apoptotic events are induced in the mutant gonads, leading to the abolishment of both spermatogenesis and oogenesis. This study provides genetic evidence that SUN1-telomere interaction is essential for telomere dynamic movement and is required for efficient homologous chromosome pairing/synapsis during mammalian gametogenesis.

SUMMARY The scarcity of tissue-specific stem cells and the complexity of their surrounding environment have made molecular characterization of these cells particularly challenging. Through single-cell transcriptome and weighted gene co-expression network analysis (WGCNA), we uncovered molecular properties of CD133+/GFAP− ependymal (E) cells in the adult mouse forebrain neurogenic zone. Surprisingly, prominent hub genes of the gene network unique to ependymal CD133+/GFAP− quiescent cells were enriched for immune-responsive genes, as well as genes encoding receptors for angiogenic factors. Administration of vascular endothelial growth factor (VEGF) activated CD133+ ependymal neural stem cells (NSCs), lining not only the lateral but also the fourth ventricles and, together with basic fibroblast growth factor (bFGF), elicited subsequent neural lineage differentiation and migration. This study revealed the existence of dormant ependymal NSCs throughout the ventricular surface of the CNS, as well as signals abundant after injury for their activation.

Nuclear movement relative to cell bodies is a fundamental process during certain aspects of mammalian retinal development. During the generation of photoreceptor cells in the cell division cycle, the nuclei of progenitors oscillate between the apical and basal surfaces of the neuroblastic layer (NBL). This process is termed interkinetic nuclear migration (INM). Furthermore, newly formed photoreceptor cells migrate and form the outer nuclear layer (ONL). In the current study, we demonstrated that a KASH domain-containing protein, Syne-2/Nesprin-2, as well as SUN domain-containing proteins, SUN1 and SUN2, play critical roles during INM and photoreceptor cell migration in the mouse retina. A deletion mutation of Syne-2/Nesprin-2 or double mutations of Sun1 and Sun2 caused severe reduction of the thickness of the ONL, mislocalization of photoreceptor nuclei and profound electrophysiological dysfunction of the retina characterized by a reduction of a- and b-wave amplitudes. We also provide evidence that Syne-2/Nesprin-2 forms complexes with either SUN1 or SUN2 at the nuclear envelope to connect the nucleus with dynein/dynactin and kinesin molecular motors during the nuclear migrations in the retina. These key retinal developmental signaling results will advance our understanding of the mechanism of nuclear migration in the mammalian retina.

Confined to one cell: A method to detect and isolate single circulating melanoma cells (CMCs; see figure) has been produced by integrating a polymer‐nanofiber‐embedded nanovelcro cell‐affinity assay with a laser microdissection (LMD) technique. This method is able to separate CMCs from normal white blood cells (WBCs) and sequence individual cells for a specific mutation related to cancer progression, allowing for more personalized cancer therapy.