Chrnb1

Acetylcholine receptor subunit beta

Spatial tier: RESTRICTED · Class: ION_CHANNEL · Top region: ME (Median eminence) · Positive regions: 20/554

42.4Discovery Score
34.9Targetability Score
CEvidence grade C
What this means: Chrnb1: fine CCF profile is restricted toward ME (top regions: ME, NLOT1, LM, MMd, ENTl1; 20 positive regions); direct spatial validation is still required.

Function in ME: evidence, prediction, innovation

Gene function
CHRNB1 encodes the beta-1 subunit of the muscle-type nicotinic acetylcholine receptor, an obligatory component of the pentameric (alpha1)2-beta1-delta-epsilon receptor at the neuromuscular junction. It is not a component of neuronal nicotinic receptors, which use beta-2 and beta-4. Mutations in CHRNB1 cause congenital myasthenic syndromes, and the receptor is the autoantigen of myasthenia gravis and the target of curare-like neuromuscular blockers.
Region function
The median eminence is the neurohaemal circumventricular interface at the base of the hypothalamus, where tanycytes and fenestrated portal capillaries let hypophysiotropic peptides such as GnRH, TRH, CRH, GHRH and dopamine reach the anterior pituitary.
Published in this region
inferred No region-specific literature found. Low-level beta-1 nAChR mRNA and protein have been reported in rodent brain including hippocampus alongside skeletal muscle (Aishah et al. 2017), and beta-1-containing responses have been described in some central preparations (Dupuis et al. 2011), but nothing has been reported in the median eminence or in tanycytes.
Predicted function
Prediction: if beta-1 protein is genuinely present in the median eminence, the most plausible location is the tanycyte layer or the portal vascular wall rather than neurons, where a muscle-type nicotinic receptor could provide a fast cation conductance that couples cholinergic tone to tanycyte calcium signalling and hence to the permeability of the portal barrier and the release of hypophysiotropic peptides. Tanycyte-restricted Chrnb1 deletion using Rax-CreERT2, or local alpha-bungarotoxin, is predicted to blunt nicotine-evoked calcium waves in tanycytes and reduce the acute rise in portal GnRH or TRH after cholinergic stimulation; because the prior probability is low, the first requirement is alpha-bungarotoxin binding or RNAscope confirmation.
Innovation
★★★☆☆ 3/5 Wholly unstudied in this region and easy to probe with alpha-bungarotoxin, but a skeletal-muscle-restricted subunit in the median eminence is more likely to be an annotation or cross-hybridisation artefact than real biology.
Tools
Chrnb1 knockout mice (perinatally lethal, so conditional alleles are needed); alpha-bungarotoxin (fluorescent conjugates for binding studies), d-tubocurarine and pancuronium; anti-AChR antibodies from myasthenia gravis research; Rax-CreERT2 for tanycytes and Gnrh1-Cre for the terminals in ME.
References

Direct evidence located at the region

Chrnb1 Allen ISH at the CCF centroid of ME

Allen ISH experiment 75888752, section image 75725210 (section 254): the section that contains the CCF centroid of Median eminence according to the Allen image-to-atlas alignment (reference_to_image), with a 2 mm window around that point. Left: whole section, red box = window. Middle: ISH signal. Right: Allen's expression-mask view of the same window. open this image in the Allen viewer

Look it up yourself: Allen Mouse Brain ISH for Chrnb1Allen reference atlas: ME (structure 10671)ABC Atlas MERFISH viewer(in the ABC Atlas choose dataset MERFISH-C57BL6J-638850-CCF, colour cells by gene "Chrnb1" or by parcellation_substructure "ME")All genes confined to ME + 3-D brain

Direct spatial evidence

MERFISH REGION LOCATOR
ME MERFISH region locator
Real single-cell MERFISH coordinates for the ME (Median eminence) section -- our own ground-truth data, showing exactly where this region sits, independent of whether the Allen ISH section below is easy to read.

Regional expression figure

Chrnb1 regional expression profile

Predicted WMB × fine-CCF profile; not direct full-transcriptome spatial measurement.

Spatial profile

ME
0.432
NLOT1
0.294
LM
0.274
MMd
0.258
ENTl1
0.218
VISpor1
0.215
AUDd1
0.212
SSp-m1
0.208
SCzo
0.206
PRM
0.204
AUDpo1
0.201
ENTl6a
0.2
FOTU
0.199
VISl1
0.198
ENTm1
0.196
TTv
0.193
SSs1
0.192
MOp1
0.192
LING
0.191
IPR
0.19

Evidence and specificity

Evidence status
PREDICTED_FINE
Direct sources
None; predicted localization only
Exclusive threshold
12 positive regions out of 554
Spatial specificity
0.282
Top-region fraction
0.061
Filter status
PASS

Interpretation limits