Scnn1b

Epithelial sodium channel subunit beta (Amiloride-sensitive sodium channel subunit beta) (Beta-NaCH) (Epithelial Na(+) channel subunit beta) (Beta-ENaC) (Nonvoltage-gated sodium channel 1 subunit beta

Spatial tier: RESTRICTED · Class: ION_CHANNEL · Top region: RO (Nucleus raphe obscurus) · Positive regions: 15/554

47.6Discovery Score
38.2Targetability Score
CEvidence grade C
What this means: Scnn1b: fine CCF profile is restricted toward RO (top regions: RO, FOTU, PRM, PYR, PRE; 15 positive regions); direct spatial validation is still required.

Function in RO: evidence, prediction, innovation

Gene function
Scnn1b encodes the beta subunit of the epithelial sodium channel (ENaC). With the alpha and gamma subunits it forms a constitutively open, amiloride-sensitive, highly sodium-selective channel regulated by aldosterone and by proteolytic cleavage. In kidney, lung and colon it sets sodium reabsorption; mutations cause Liddle syndrome and pseudohypoaldosteronism.
Region function
Nucleus raphe obscurus is the caudal medullary raphe serotonergic cell group; it projects to spinal cord and to respiratory and motor nuclei and contributes to central CO2/pH chemoreception, thermoregulation and autonomic and motor tone.
Published in this region
inferred No region-specific literature found. The closest findings are that serotonergic medullary neurons near the area postrema are activated by raised plasma sodium and relay this interoceptive signal forward (Miller 2014), while da Silva 2013 showed raphe obscurus 5-HT neurons are not required for hypoxic ventilatory and thermoregulatory responses; ENaC subunits themselves have been studied in sodium-sensing circumventricular tissue rather than in raphe obscurus.
Predicted function
Prediction: in raphe obscurus, beta-ENaC would supply a tonic sodium leak that sets the resting potential and spontaneous pacemaker firing of 5-HT neurons and would make their firing rate track CSF sodium and osmolality in addition to CO2 and pH. Local amiloride or benzamil, or deletion of Scnn1b in Pet1/Tph2-defined neurons, is predicted to hyperpolarise these cells, reduce tonic serotonergic drive to spinal motor and respiratory circuits, and blunt sodium-appetite and ventilatory responses to hypernatraemia while leaving the hypoxic response unchanged.
Innovation
★★★★★ 5/5 A sodium-leak channel in a serotonergic chemosensory nucleus is a mechanistically attractive and completely unexamined idea, and floxed Scnn1b plus Pet1/Tph2 drivers make it immediately testable.
Tools
Scnn1b floxed and Liddle-syndrome transgenic mice; amiloride and benzamil as blockers; anti-beta-ENaC antibodies; raphe 5-HT neurons targetable with Pet1-Flpe, Tph2-CreERT2 and Slc6a4-Cre.
References

Direct evidence located at the region

Scnn1b Allen ISH at the CCF centroid of RO

Allen ISH experiment 69288321, section image 69244852 (section 136): the section that contains the CCF centroid of Nucleus raphe obscurus 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 Scnn1bAllen reference atlas: RO (structure 222)ABC Atlas MERFISH viewer(in the ABC Atlas choose dataset MERFISH-C57BL6J-638850-CCF, colour cells by gene "Scnn1b" or by parcellation_substructure "RO")All genes confined to RO + 3-D brain

Direct spatial evidence

MERFISH REGION LOCATOR
RO MERFISH region locator
Real single-cell MERFISH coordinates for the RO (Nucleus raphe obscurus) 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

Scnn1b regional expression profile

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

Spatial profile

RO
0.402
FOTU
0.153
PRM
0.142
PYR
0.138
PRE
0.137
RPA
0.136
ANcr2
0.121
DEC
0.117
ANcr1
0.116
POST
0.112
LING
0.11
SIM
0.102
PFL
0.0986
CUL4, 5
0.0921
PG
0.0898
NOD
0.0887
FL
0.0882
x
0.0864
COPY
0.0858
CENT2
0.0846

Evidence and specificity

Evidence status
PREDICTED_FINE
Direct sources
None; predicted localization only
Exclusive threshold
12 positive regions out of 554
Spatial specificity
0.369
Top-region fraction
0.106
Filter status
PASS

Interpretation limits