Secular Trends in Adherence to Healthy Behaviors Among US Adults with Diabetes, 1999-2018.

Adherence to healthy lifestyle is essential for diabetes management in light of the plateaued metabolic control, diversifying causes of death, and continued excess mortality among people with diabetes (PWD). This study aims to assess the secular trend of adherence to healthy behaviors among PWD in NHANES, a nationally representative survey of Americans using a stratified, multistage probability design in 2-year cycles since 1999. Adherence to healthy lifestyle was estimated using never smoking, moderate drinking, adequate physical activity, and healthy diet, and the score ranged 0-4. Among 7410 participants, adherence to healthy behaviors across time slightly increased from 1.4 (95% CI, 1.3 to 1.5) in 1999-2002 to 1.6 (1.5 to 1.8) in 2015-2018 (Ptrend = 0.002). The non-Hispanic Blacks caught up with the non-Hispanic Whites in overall lifestyle score (1.7 vs. 1.6 in 2015-2018), while large socioeconomic disparities remained in that participants with higher income and education level, and covered by health insurance were more likely to have adherence to healthy behaviors. As the metabolic control plateaued and causes of death have diversified among PWD, our findings suggested a great potential of lifestyle modification in facilitating the long-term health of these patients.

The CTNNBIP1-CLSTN1 fusion transcript regulates human neocortical development.

Fusion transcripts or RNAs have been found in both disordered and healthy human tissues and cells; however, their physiological functions in the brain development remain unknown. In the analysis of deposited RNA-sequence libraries covering early to middle embryonic stages, we identify 1,055 fusion transcripts present in the developing neocortex. Interestingly, 98 fusion transcripts exhibit distinct expression patterns in various neural progenitors (NPs) or neurons. We focus on CTNNBIP1-CLSTN1 (CTCL), which is enriched in outer radial glial cells that contribute to cortex expansion during human evolution. Intriguingly, downregulation of CTCL in cultured human cerebral organoids causes marked reduction in NPs and precocious neuronal differentiation, leading to impairment of organoid growth. Furthermore, the expression of CTCL fine-tunes Wnt/ß-catenin signaling that controls cortex patterning. Together, this work provides evidence indicating important roles of fusion transcript in human brain development and evolution.

Single-cell transcriptomes reveal molecular specializations of neuronal cell types in the developing cerebellum.

The cerebellum is critical for controlling motor and non-motor functions via cerebellar circuit that is composed of defined cell types, which approximately account for more than half of neurons in mammals. The molecular mechanisms controlling developmental progression and maturation processes of various cerebellar cell types need systematic investigation. Here, we analyzed transcriptome profiles of 21119 single cells of the postnatal mouse cerebellum and identified eight main cell clusters. Functional annotation of differentially expressed genes revealed trajectory hierarchies of granule cells (GCs) at various states and implied roles of mitochondrion and ATPases in the maturation of Purkinje cells (PCs), the sole output cells of the cerebellar cortex. Furthermore, we analyzed gene expression patterns and co-expression networks of 28 ataxia risk genes, and found that most of them are related with biological process of mitochondrion and around half of them are enriched in PCs. Our results also suggested core transcription factors that are correlated with interneuron differentiation and characteristics for the expression of secretory proteins in glia cells, which may participate in neuronal modulation. Thus, this study presents a systematic landscape of cerebellar gene expression in defined cell types and a general gene expression framework for cerebellar development and dysfunction.

The hominoid-specific gene TBC1D3 promotes generation of basal neural progenitors and induces cortical folding in mice.

Cortical expansion and folding are often linked to the evolution of higher intelligence, but molecular and cellular mechanisms underlying cortical folding remain poorly understood. The hominoid-specific gene TBC1D3 undergoes segmental duplications during hominoid evolution, but its role in brain development has not been explored. Here, we found that expression of TBC1D3 in ventricular cortical progenitors of mice via in utero electroporation caused delamination of ventricular radial glia cells (vRGs) and promoted generation of self-renewing basal progenitors with typical morphology of outer radial glia (oRG), which are most abundant in primates. Furthermore, down-regulation of TBC1D3 in cultured human brain slices decreased generation of oRGs. Interestingly, localized oRG proliferation resulting from either in utero electroporation or transgenic expression of TBC1D3, was often found to underlie cortical regions exhibiting folding. Thus, we have identified a hominoid gene that is required for oRG generation in regulating the cortical expansion and folding.

Semaphorin 3A activates the guanosine triphosphatase Rab5 to promote growth cone collapse and organize callosal axon projections.

Axon guidance (pathfinding) wires the brain during development and is regulated by various attractive and repulsive cues. Semaphorin 3A (Sema3A) is a repulsive cue, inducing the collapse of axon growth cones. In the mammalian forebrain, the corpus callosum is the major commissure that transmits information flow between the two hemispheres, and contralateral axons assemble into well-defined tracts. We found that the patterning of callosal axon projections in rodent layer II and III (L2/3) cortical neurons in response to Sema3A was mediated by the activation of Rab5, a small guanosine triphosphatase (GTPase) that mediates endocytosis, through the membrane fusion protein Rabaptin-5 and the Rab5 guanine nucleotide exchange factor (GEF) Rabex-5. Rabaptin-5 bound directly to Plexin-A1 in the Sema3A receptor complex [an obligate heterodimer formed by Plexin-A1 and neuropilin 1 (NP1)]; Sema3A enhanced this interaction in cultured neurons. Rabaptin-5 bridged the interaction between Rab5 and Plexin-A1. Sema3A stimulated endocytosis from the cell surface of callosal axon growth cones. In utero electroporation to reduce Rab5 or Rabaptin-5 impaired axon fasciculation or caused mistargeting of L2/3 callosal projections in rats. Overexpression of Rabaptin-5 or Rab5 rescued the defective callosal axon fasciculation or mistargeting of callosal axons caused by the loss of Sema3A-Plexin-A1 signaling in rats expressing dominant-negative Plexin-A1 or in NP1-deficient mice. Thus, our findings suggest that Rab5, its effector Rabaptin-5, and its regulator Rabex-5 mediate Sema3A-induced axon guidance during brain development.

Nuclear factor kappaB controls acetylcholine receptor clustering at the neuromuscular junction.

At the vertebrate neuromuscular junction (NMJ), acetylcholine receptor (AChR) clustering is stimulated by motor neuron-derived glycoprotein Agrin and requires a number of intracellular signal or structural proteins, including AChR-associated scaffold protein Rapsyn. Here, we report a role of nuclear factor kappaB (NF-kappaB), a well known transcription factor involved in a variety of immune responses, in regulating AChR clustering at the NMJ. We found that downregulating the expression of RelA/p65 subunit of NF-kappaB or inhibiting NF-kappaB activity by overexpression of mutated form of IkappaB (inhibitor kappaB), which is resistant to proteolytic degradation and thus constitutively keeps NF-kappaB inactive in the cytoplasma, impeded the formation of AChR clusters in cultured C2C12 muscle cells stimulated by Agrin. In contrast, overexpression of RelA/p65 promoted AChR clustering. Furthermore, we investigated the mechanism by which NF-kappaB regulates AChR clustering. Interestingly, we found that downregulating the expression of RelA/p65 caused a marked reduction in the protein and mRNA level of Rapsyn and upregulation of RelA/p65 enhanced Rapsyn promoter activity. Mutation of NF-kappaB binding site on Rapsyn promoter prevented responsiveness to RelA/p65 regulation. Moreover, forced expression of Rapsyn in RelA/p65 downregulated muscle cells partially rescued AChR clusters, suggesting that NF-kappaB regulates AChR clustering, at least partially through the transcriptional regulation of Rapsyn. In line with this notion, genetic ablation of RelA/p65 selectively in the skeletal muscle caused a reduction of AChR density at the NMJ and a decrease in the level of Rapsyn. Thus, NF-kappaB signaling controls AChR clustering through transcriptional regulation of synaptic protein Rapsyn.

Mechanism underlying activity-dependent insertion of TrkB into the neuronal surface.

Activity-dependent insertion of tyrosine kinase receptor type 2 (TrkB receptor) into the plasma membrane can explain, in part, the preferential effect of brain-derived neurotrophic factor (BDNF) on active neurons; however, the detailed cellular and molecular mechanisms underlying this process are still unclear. In our study, we developed a fluorescence ratiometric assay for surface TrkB receptors to investigate the mechanisms of recruitment of TrkB to the plasma membrane following chemical long-term potentiation (cLTP) induction. We found that, in hippocampal neurons, the effect of cLTP-induced TrkB surface-recruitment occurred predominantly on neurites with rapid kinetics (t(1/2) of approximately 2.3 minutes) and was dependent on an intact cytoskeleton structure. Mutagenesis studies revealed that the juxtamembrane domain of TrkB is necessary and sufficient for its activity-dependent insertion into the plasma membrane. Moreover, we found that the phosphorylation of TrkB receptor at the Ser478 site by cyclin-dependent kinase 5 (Cdk5) is essential for cLTP-induced TrkB insertion into the neuronal surface. Finally, the degree of cLTP-induced TrkB surface-recruitment is higher in postsynaptic regions, which provides a potential mechanism for rapid enhancement of postsynaptic sensitivity to incoming BDNF signaling. Our studies provide new insights regarding neuronal activity-dependent surface delivery of TrkB receptor, which will advance our understanding of the modulatory role of TrkB in synaptic plasticity.

GDNF isoform affects intracellular trafficking and secretion of GDNF in neuronal cells.

Glial cell line derived neurotrophic factor (GDNF) plays a critical role in central and peripheral neuron survival and function. In human and rodents, GDNF exists in an alternative spliced isoform (GDNF Delta 78), which has a 78 bp deletion in the pro-region of the GDNF encoding sequence. Whether the GDNF isoform affects GDNF function is unknown. Here, we investigated the secretion and intracellular localization of the GDNF Delta 78 isoform in neuronal cell populations. Our data indicate that a decreased secretion and an abnormal intracellular distribution of GDNF Delta 78 occurred in neuronal cells. The colocalization studies revealed much more localization of GDNF Delta 78 with Golgi marker-TGN38, which indicates that the accumulation of GDNF Delta 78 in the Golgi apparatus might in part account for its intracellular trafficking and secretion deficit. To our knowledge, it is reported for the first time that the GDNF Delta 78 isoform has a deficit in GDNF intracellular trafficking and secretion.