Probes for INS

The unique mental abilities of humans are rooted in the immensely expanded and folded neocortex, which reflects the expansion of neural progenitors, especially basal progenitors including basal radial glia (bRGs) and intermediate progenitor cells (IPCs). We found that constitutively active Sonic hedgehog (Shh) signaling expanded bRGs and IPCs and induced folding in the otherwise smooth mouse neocortex, whereas the loss of Shh signaling decreased the number of bRGs and IPCs and the size of the neocortex. SHH signaling was strongly active in the human fetal neocortex but Shh signaling was not strongly active in the mouse embryonic neocortex, and blocking SHH signaling in human cerebral organoids decreased the number of bRGs. Mechanistically, Shh signaling increased the initial generation and self-renewal of bRGs and IPC proliferation in mice and the initial generation of bRGs in human cerebral organoids. Thus, robust SHH signaling in the human fetal neocortex may contribute to bRG and IPC expansion and neocortical growth and folding.

The arginine-vasopressin (AVP)-containing hypothalamic magnocellular neurosecretory neurons (VPMNNs) are known for their role in hydro-electrolytic balance control via their projections to the neurohypophysis. Recently, projections from these same neurons to hippocampus, habenula and other brain regions in which vasopressin infusion modulates contingent social and emotionally-affected behaviors, have been reported. Here, we present evidence that VPMNN collaterals also project to the amygdaloid complex, and establish synaptic connections with neurons in central amygdala (CeA). The density of AVP innervation in amygdala was substantially increased in adult rats that had experienced neonatal maternal separation (MS), consistent with our previous observations that MS enhances VPMNN number in the paraventricular (PVN) and supraoptic (SON) nuclei of the hypothalamus. In the CeA, V1a AVP receptor mRNA was only observed in GABAergic neurons, demonstrated by complete co-localization of V1a transcripts in neurons expressing Gad1 and Gad2 transcripts in CeA using the RNAscope method. V1b and V2 receptor mRNAs were not detected, using the same method. Water-deprivation (WD) for 24 h, which increased the metabolic activity of VPMNNs, also increased anxiety-like behavior measured using the elevated plus maze (EPM) test, and this effect was mimicked by bilateral microinfusion of AVP into the CeA. Anxious behavior induced by either WD or AVP infusion was reversed by CeA infusion of V1a antagonist. VPMNNs are thus a newly discovered source of CeA inhibitory circuit modulation, through which both early-life and adult stress coping signals are conveyed from the hypothalamus to the amygdala.

Loss of bladder control is common after spinal cord injury (SCI) and no causal therapies are available. Here we investigated if function blocking antibodies against the nerve fiber growth inhibitory protein Nogo-A applied to rats with severe SCI could prevent development of neurogenic lower urinary tract dysfunction. Bladder function of rats with SCI was repeatedly assessed by urodynamic examination in fully awake animals. Four weeks after SCI, detrusor sphincter dyssynergia had developed in all untreated or control antibody infused animals. In contrast, 2 weeks of intrathecal anti-Nogo-A-antibody treatment led to a significantly reduced aberrant maximum detrusor pressure during voiding and a reduction of the abnormal EMG high frequency activity in the external urethral sphincter. Anatomically, we found higher densities of fibers originating from the pontine micturition center in the lumbo-sacral grey matter in the anti-Nogo-A antibody treated animals, as well as a reduced number of inhibitory interneurons in Lamina X These results suggest that anti-Nogo-A therapy could have positive effects on bladder function also clinically.Significance Statement:Bladder function is after spinal cord injury completely out of control. Detrusor sphincter dyssynergia, a potentially live threatening consequence, is greatly feared. Currently there are only symptomatic treatment options available and first causal treatment options are urgently needed in humans. In this work we show that function blocking antibodies against the nerve fiber growth inhibitory protein Nogo-A applied to rats with severe spinal cord injury could prevent development of neurogenic lower urinary tract dysfunction, in particular detrusor sphincter dyssynergia. Anti-Nogo-A therapy enters currently phase II clinical trial in humans and might therefore be soon the first causal treatment option for neurogenic lower urinary tract dysfunction.

To understand how proper circuit formation and function is established in the mammalian brain, it is necessary to define the genes and signaling pathways that instruct excitatory and inhibitory synapse development. We previously demonstrated that the ligand-receptor pair, Sema4D and Plexin-B1, regulates inhibitory synapse development on an unprecedentedly fast time-scale while having no effect on excitatory synapse development. Here, we report previously undescribed synaptogenic roles for Sema4A and Plexin-B2 and provide new insight into Sema4D and Plexin-B1 regulation of synapse development in rodent hippocampus. First, we show that Sema4a, Sema4d, Plxnb1, and Plxnb2 have distinct and overlapping expression patterns in neurons and glia in the developing hippocampus. Second, we describe a requirement for Plexin-B1 in both the presynaptic axon of inhibitory interneurons as well as the postsynaptic dendrites of excitatory neurons for Sema4D-dependent inhibitory synapse development. Third, we define a new synaptogenic activity for Sema4A in mediating inhibitory and excitatory synapse development. Specifically, we demonstrate that Sema4A signals through the same pathway as Sema4D, via the postsynaptic Plexin-B1 receptor, to promote inhibitory synapse development. However, Sema4A also signals through the Plexin-B2 receptor to promote excitatory synapse development. Our results shed new light on the molecular cues that promote the development of either inhibitory or excitatory synapses in the mammalian hippocampus.