| Topic | Key facts | Source (year) | DOI / URL | Evidence citation |
|---|---|---|---|---|
| Definition / core phenotype | EAST syndrome = **Epilepsy, Ataxia, Sensorineural deafness, Tubulopathy**; SeSAME = **Seizures, Sensorineural deafness, Ataxia, Mental/Intellectual disability, Electrolyte imbalance**. Rare multisystem disorder with neurologic, renal, and auditory involvement. | Reichold et al. 2010; Fracaro et al. 2024 | https://doi.org/10.1073/pnas.1003072107 ; https://doi.org/10.3390/app14124985 | (pqac-00000020, pqac-00000021) |
| Causative gene / protein | Caused by **biallelic loss-of-function variants in KCNJ10**, encoding the inwardly rectifying potassium channel **Kir4.1**; gene located on **chromosome 1q22-23**. | Reichold et al. 2010; Fracaro et al. 2024 | https://doi.org/10.1073/pnas.1003072107 ; https://doi.org/10.3390/app14124985 | (pqac-00000019, pqac-00000021) |
| Inheritance | **Autosomal recessive** disorder; several reported families are consanguineous. | Reichold et al. 2010; Fracaro et al. 2024 | https://doi.org/10.1073/pnas.1003072107 ; https://doi.org/10.3390/app14124985 | (pqac-00000019, pqac-00000003, pqac-00000021) |
| Key renal electrolyte abnormalities | Gitelman-like salt-wasting tubulopathy with **urinary Na+ loss, RAAS activation, hypokalemic metabolic alkalosis, hypomagnesemia, and hypocalciuria**. | Reichold et al. 2010 | https://doi.org/10.1073/pnas.1003072107 | (pqac-00000019, pqac-00000009, pqac-00000020) |
| Renal mechanism | Kir4.1/KCNJ10 is expressed in the **basolateral membrane of distal convoluted tubule (DCT), connecting tubule, and cortical collecting duct**; with KCNJ16/Kir5.1 it supports **K+ recycling / pump-leak coupling**, sustaining Na+/K+-ATPase activity and distal transport. Loss reduces reabsorptive capacity and causes salt wasting. | Reichold et al. 2010; Gondra et al. 2026 preprint | https://doi.org/10.1073/pnas.1003072107 ; https://doi.org/10.64898/2026.01.07.25343066 | (pqac-00000019, pqac-00000008, pqac-00000006) |
| Renal structural correlate | Patient renal biopsy EM showed **reduced basolateral infoldings** (and decreased mitochondria in DCT cells in summarized evidence), consistent with impaired salt reabsorption. | Reichold et al. 2010 | https://doi.org/10.1073/pnas.1003072107 | (pqac-00000008, pqac-00000019) |
| Auditory mechanism | Kir4.1 is critical for **cochlear K+ recycling** and **generation/maintenance of the endocochlear potential**; loss in strial intermediate cells disrupts endolymph homeostasis and contributes to **sensorineural hearing loss**. Hearing loss severity ranges from mild to severe. | Fracaro et al. 2024 | https://doi.org/10.3390/app14124985 | (pqac-00000017, pqac-00000000, pqac-00000003) |
| Neurologic mechanism | Kir4.1 dysfunction in **brain glia/astrocytes** impairs extracellular **K+ spatial buffering**, promoting neuronal hyperexcitability and epilepsy/ataxia. | Fracaro et al. 2024; contextual mechanistic evidence | https://doi.org/10.3390/app14124985 | (pqac-00000021, pqac-00000000) |
| Ophthalmic / physiologic implementation | Human ERG studies in **4 unrelated EAST patients** showed reduced **photopic negative response** and reduced retinal sensitivity, confirming Kir4.1 contribution to human retinal physiology. | Thompson et al. 2011 | https://doi.org/10.1113/jphysiol.2010.198531 | (pqac-00000018) |
| Variant set studied functionally in landmark paper | **R65P, G77R, R175Q, R199X** were tested in heterologous systems; all caused partial or complete channel dysfunction, with **R199X complete loss-of-function**. | Reichold et al. 2010 | https://doi.org/10.1073/pnas.1003072107 | (pqac-00000008, pqac-00000009, pqac-00000012) |
| Single-channel functional results | WT open probability ~**70–80%**; **R65P ~20–30%**, **R175Q ~10–15%**, **G77R ~0.5% / nearly inactive**. Mutants showed flickering and reduced mean open time; whole-cell Ba2+-sensitive currents were markedly reduced. | Reichold et al. 2010 | https://doi.org/10.1073/pnas.1003072107 | (pqac-00000012, pqac-00000010) |
| pH sensitivity shift | WT KCNJ10 pH IC50 ~**6.3**; **R65P shifted to ~7.8** and **R175Q to ~9.35**, indicating a marked **alkaline shift** in pH sensitivity. Authors note metabolic alkalosis in R65P patients might partially improve residual function. | Reichold et al. 2010 | https://doi.org/10.1073/pnas.1003072107 | (pqac-00000019, pqac-00000009, pqac-00000012) |
| PIP2 affinity defect | **R175Q** showed markedly reduced **PIP2 affinity**, with poly-Lys inhibition time constant **0.47 ± 0.1 s** vs WT **17.89 ± 3.1 s**. | Reichold et al. 2010 | https://doi.org/10.1073/pnas.1003072107 | (pqac-00000010) |
| Additional notable variants in later reviews / summaries | Additional EAST/SeSAME-associated variants discussed include **A167V**, **R297C**, **T164I**, **G83V**, **L166Q**, and frameshifts **Asn232Glnfs*14** and **Gly275Valfs*7**. | Fracaro et al. 2024; Gür et al. 2025 | https://doi.org/10.3390/app14124985 ; https://doi.org/10.1186/s43042-025-00800-w | (pqac-00000003, pqac-00000002) |
| Functional notes for additional variants | **R65P, T164I, R297C** alter pH sensing/pore gating; **G77R** likely alters channel structure/gating; **A167V** may reduce surface expression (especially with R297C); **G83V** and **L166Q** are reported to reduce or abolish channel activity in cited functional work. Truncating variants **Asn232Glnfs*14** and **Gly275Valfs*7** are predicted to cause more severe consequences, including severe epilepsy/tubulopathy. | Fracaro et al. 2024; Gür et al. 2025 | https://doi.org/10.3390/app14124985 ; https://doi.org/10.1186/s43042-025-00800-w | (pqac-00000003, pqac-00000002) |
| Mutation burden / phenotypic variability | Review summary notes **16 KCNJ10 mutations** reported, with **variable intrafamilial phenotypes**; seizures typically begin in **early childhood**, hearing loss ranges **mild to severe**. | Fracaro et al. 2024 | https://doi.org/10.3390/app14124985 | (pqac-00000000, pqac-00000017) |
| Diagnostic implication | **KCNJ10 sequencing** is central for diagnosis in individuals with the EAST/SeSAME phenotype; real-world differential diagnosis often overlaps with **Gitelman/Bartter-like tubulopathies** and syndromic deafness. | Fracaro et al. 2024; Reichold et al. 2010 | https://doi.org/10.3390/app14124985 ; https://doi.org/10.1073/pnas.1003072107 | (pqac-00000017, pqac-00000019) |


*Table: This table condenses the core clinical, genetic, mechanistic, and variant-function evidence for EAST/SeSAME syndrome from the retrieved literature. It is designed as a quick reference for disease definition, Kir4.1 biology, hallmark electrolyte abnormalities, and mutation-specific functional effects.*