Kcnh8

Voltage-gated delayed rectifier potassium channel KCNH8 (Ether-a-go-go-like potassium channel 3) (ELK channel 3) (ELK3) (Potassium voltage-gated channel subfamily H member 8) (Voltage-gated potassium

Spatial tier: RESTRICTED · Class: ION_CHANNEL · Top region: SCH (Suprachiasmatic nucleus) · Positive regions: 26/554

43.7Discovery Score
42.8Targetability Score
CEvidence grade C
What this means: Kcnh8: fine CCF profile is restricted toward SCH (top regions: SCH, MH, SBPV, PVa, LH; 26 positive regions); direct spatial validation is still required.

Function in SCH: evidence, prediction, innovation

Gene function
Kcnh8 encodes Kv12.1 (ELK3), a subthreshold-activating delayed-rectifier potassium channel of the EAG/KCNH family. Because it opens near the resting membrane potential rather than during the spike, it acts as a brake on spontaneous firing and sets how readily a neuron fires repetitively, rather than repolarising individual action potentials.
Region function
The suprachiasmatic nucleus above the optic chiasm is the master circadian pacemaker; it receives retinal input via the retinohypothalamic tract and imposes roughly 24-hour rhythms on sleep-wake, hormone release and body temperature through a large day-night swing in the spontaneous firing rate of its neurons.
Published in this region
direct Direct. Hermanstyne 2023 recorded SCN neurons in slices from Kcnh8-null (Kv12.1-/-) and Kcnh3-null (Kv12.2-/-) mice and found that night-time repetitive firing rates were elevated while daytime rates were unchanged, so the hallmark day-night difference in SCN firing was eliminated; in vivo shRNA knockdown of Kv12.1 in adult SCN reproduced the effect. The bioRxiv preprint (Hermanstyne 2023) reports the same result. This identifies Kv12-encoded channels as the long-sought subthreshold potassium conductance driving the circadian firing switch, complementing earlier work on A-type and afterhyperpolarisation currents in SCN (Itri 2010; Jackson 2004).
Predicted function
Prediction: Kv12.1 is the night-time brake on SCN pacemaking, so restricting its deletion to Vip- or Avp-expressing SCN neurons should selectively raise night firing in that subpopulation, flatten the electrical rhythm, and reduce behavioural rhythm amplitude or alter free-running period and re-entrainment speed in constant darkness. Conversely, a Kv12 opener applied to SCN should deepen night-time quiescence and increase rhythm amplitude. Because Kv12.1 and Kv12.2 knockouts give the same phenotype, the two subunits probably co-assemble, predicting that a double knockout will be no worse than either single.
Innovation
★★☆☆☆ 2/5 This gene-region pair has already been nailed down functionally, leaving cell-type-specific and behavioural consequences as the remaining gap.
Tools
Kcnh8 (Kv12.1-/-) and Kcnh3 (Kv12.2-/-) knockout mice plus shRNA constructs validated in adult SCN; SCN cell types accessible with Vip-IRES-Cre (JAX 010908) and Avp-IRES2-Cre (JAX 023530); PER2::LUC reporter mice for rhythm readout; no selective small-molecule Kv12.1 blocker in common use.
References

Direct evidence located at the region

Kcnh8 Allen ISH at the CCF centroid of SCH

Allen ISH experiment 70562113, section image 70435357 (section 313): the section that contains the CCF centroid of Suprachiasmatic nucleus 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 Kcnh8Allen reference atlas: SCH (structure 286)ABC Atlas MERFISH viewer(in the ABC Atlas choose dataset MERFISH-C57BL6J-638850-CCF, colour cells by gene "Kcnh8" or by parcellation_substructure "SCH")All genes confined to SCH + 3-D brain

Direct spatial evidence

MERFISH REGION LOCATOR
SCH MERFISH region locator
Real single-cell MERFISH coordinates for the SCH (Suprachiasmatic nucleus) 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

Kcnh8 regional expression profile

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

Spatial profile

SCH
5.82
MH
5.25
SBPV
3.5
PVa
3.26
LH
2.83
PD
2.82
PDTg
2.71
ARH
2.68
MMm
2.67
VMPO
2.66
PVpo
2.56
MMp
2.55
PVT
2.49
PS
2.42
ADP
2.34
PMd
2.32
MMl
2.28
MPO
2.02
MEPO
2.01
AVPV
1.98

Evidence and specificity

Evidence status
PREDICTED_FINE
Direct sources
None; predicted localization only
Exclusive threshold
12 positive regions out of 554
Spatial specificity
0.315
Top-region fraction
0.061
Filter status
PASS

Interpretation limits