PROJECT STRANDSHIFT | POLYQ DISEASE COMPARATIVE ATLAS

Phase 0 — Disease Intelligence & Comparative Positioning

Program: PROJECT STRANDSHIFT

Classification: Polyglutamine Repeat Expansion Disease Comparative Atlas

Primary Disease Anchor: Huntington Disease

Comparative Disease Class: PolyQ Neurodegenerative Disorders

1. Objective

To compare Huntington disease against major polyglutamine disorders by mapping shared and divergent mechanisms involving CAG repeat expansion, mutant protein toxicity, somatic instability, DNA repair modifiers, neuroimmune activation, mitochondrial dysfunction, apoptosis, and disease-region vulnerability.

2. PolyQ Disease Family Overview

Polyglutamine diseases are inherited neurodegenerative disorders caused by expanded CAG repeats within protein-coding regions. These expansions produce elongated polyglutamine tracts that alter protein folding, disrupt cellular networks, and promote progressive neuronal dysfunction.

Disease	Gene	Protein	Primary CNS Vulnerability
Huntington Disease	HTT	Huntingtin	Striatum, cortex
SCA1	ATXN1	Ataxin-1	Cerebellum, brainstem
SCA2	ATXN2	Ataxin-2	Cerebellum, brainstem
SCA3 / Machado-Joseph Disease	ATXN3	Ataxin-3	Cerebellum, basal ganglia
SCA6	CACNA1A	Calcium channel subunit	Cerebellum
SCA7	ATXN7	Ataxin-7	Cerebellum, retina
DRPLA	ATN1	Atrophin-1	Cerebellum, basal ganglia
SBMA / Kennedy Disease	AR	Androgen receptor	Motor neurons, muscle

3. Shared Molecular Fault Architecture

Fault Layer	Shared PolyQ Mechanism	STRANDSHIFT Interpretation
Genetic Initiation	CAG repeat expansion	inherited disease trigger
Protein Toxicity	polyglutamine elongation	misfolding and aggregation
Proteostasis Failure	chaperone overload, impaired clearance	toxic protein accumulation
Transcriptional Dysregulation	altered gene-expression control	network destabilization
Mitochondrial Stress	ATP loss, ROS elevation	energy collapse
DNA Repair Interaction	repeat instability modifiers	somatic expansion risk
Neuroimmune Activation	glial activation, cytokines	inflammatory amplification
Cell Fate Failure	apoptosis, senescence	neuronal loss

4. Disease-by-Disease Comparative Matrix

Disease	Primary Phenotype	PolyQ Mechanism	Key STRANDSHIFT Relevance
Huntington Disease	chorea, cognitive decline, psychiatric symptoms	mutant HTT toxicity and somatic CAG expansion	anchor disease model
SCA1	ataxia, dysarthria, oculomotor dysfunction	ATXN1 nuclear toxicity	transcriptional dysfunction comparison
SCA2	ataxia, neuropathy, slow saccades	ATXN2 RNA/protein interaction disruption	RNA instability comparison
SCA3	ataxia, dystonia, neuropathy	ATXN3 proteostasis disruption	ubiquitin-proteasome comparison
SCA6	pure cerebellar ataxia	CACNA1A channel dysfunction	calcium signaling comparison
SCA7	ataxia plus retinal degeneration	ATXN7 transcription complex disruption	retina-neurodegeneration comparison
DRPLA	epilepsy, dementia, ataxia, chorea	ATN1 transcriptional toxicity	pediatric/adult phenotype comparison
SBMA	motor neuron degeneration, androgen sensitivity	AR ligand-dependent toxicity	endocrine-modulated PolyQ model

5. HTT vs Other PolyQ Disorders

Huntington disease is the STRANDSHIFT anchor because it combines a clearly defined genetic trigger with strong evidence of somatic expansion, striatal vulnerability, neuroimmune activation, psychiatric manifestations, and progressive systemic involvement.

Feature	HD	SCAs	DRPLA	SBMA
CAG expansion	Yes	Yes	Yes	Yes
Strong somatic expansion	High	variable	variable	lower/variable
Major psychiatric burden	High	variable	variable	lower
Primary movement phenotype	chorea	ataxia	chorea/ataxia	weakness
Major cortical involvement	Yes	variable	Yes	limited
Peripheral involvement	Yes	variable	variable	strong in SBMA
STRANDSHIFT priority	Highest	comparative	comparative	endocrine comparison

6. DNA Repair and Somatic Expansion Comparison

Repair Axis	HD Relevance	PolyQ-Wide Relevance
MSH3	major expansion accelerator	candidate shared modifier
MSH2	mismatch repair involvement	repeat instability contributor
MLH1	expansion pathway modulation	potential shared modifier
PMS1 / PMS2	repair complex modulation	candidate modifier network
FAN1	protective repeat-stability factor	high-value comparative target
EXO1	repeat processing	expansion biology candidate

STRANDSHIFT interpretation: PolyQ diseases may share a common repeat-instability architecture, but tissue vulnerability and gene-specific protein function determine final clinical phenotype.

7. Neuroimmune Comparison

Disease	Expected Neuroimmune Signature	Research Priority
HD	microglial activation, cytokine elevation, complement signaling	high
SCA1	cerebellar inflammatory activation	moderate
SCA2	glial activation and RNA-stress inflammation	moderate
SCA3	proteostasis-linked inflammatory stress	moderate
SCA7	retinal-neural inflammatory overlap	moderate
DRPLA	neurodevelopmental and seizure-linked inflammation	high
SBMA	motor neuron and muscle immune-metabolic stress	moderate

8. SCF–CMF Comparative Interpretation

Using the Conscience Mind Framework, PolyQ disease expression can be interpreted through six biological domains. Awareness corresponds to cognitive and sensory integration; Emotion corresponds to limbic and psychiatric vulnerability; Embodiment reflects motor system expression; Energy reflects mitochondrial and metabolic resilience; Time reflects age-dependent somatic expansion and disease progression; and Transformation reflects whether the system adapts, compensates, or degenerates.

Huntington disease shows strong disruption across all six domains, making it the most complete SCF model for PolyQ systems degeneration. Spinocerebellar ataxias emphasize Embodiment and Time through progressive motor coordination failure. DRPLA emphasizes Transformation through developmental and seizure-related phenotype shifts. SBMA emphasizes Embodiment and Energy through endocrine-sensitive motor neuron and muscle degeneration.

9. Comparative Biomarker Panel

Biomarker Class	Candidate Markers	Purpose
Repeat Burden	CAG length, somatic expansion index	disease-driving mutation load
DNA Injury	γH2AX, 53BP1, 8-OHdG	genome-stress burden
Proteostasis	ubiquitin, HSP70, HSP90, autophagy markers	protein-clearance failure
Neuroimmune	IL-6, TNF-α, IL-1β, C3, TREM2	inflammatory amplification
Mitochondrial	ATP, PGC-1α, TFAM, SOD2	energy resilience
Cell Fate	TP53, BAX/BCL2, caspase-3	apoptosis transition
Clinical	motor, cognitive, psychiatric, functional scales	phenotype mapping

10. STRANDSHIFT Comparative Hypotheses

Hypothesis 1: PolyQ diseases share a common repeat-expansion and proteotoxic architecture, but disease-specific protein function determines tissue vulnerability.

Hypothesis 2: DNA repair modifiers such as MSH3 and FAN1 may represent cross-PolyQ therapeutic leverage points.

Hypothesis 3: Neuroimmune activation is a disease amplifier across PolyQ disorders, but its intensity differs by affected tissue and disease stage.

Hypothesis 4: Mitochondrial dysfunction and oxidative DNA injury form a shared degeneration bridge across the PolyQ family.

Hypothesis 5: Huntington disease is the most complete model for integrating somatic expansion, neuroimmune activation, psychiatric burden, and systems-level degeneration.

11. Therapeutic Positioning

Therapeutic Strategy	HD	Other PolyQ Disorders	SCF Priority
mutant protein lowering	high	gene-specific	highest
somatic expansion suppression	high	disease-dependent	high
FAN1 enhancement	high	exploratory	high
MSH3 modulation	high	exploratory	high
proteostasis restoration	high	high	high
mitochondrial restoration	high	high	high
neuroimmune modulation	high	moderate-high	high
synaptic resilience	high	high	high

12. Conclusion

The PolyQ Disease Comparative Atlas positions Huntington disease as the central STRANDSHIFT model for studying inherited CAG repeat expansion, somatic genomic instability, proteotoxicity, neuroimmune amplification, mitochondrial collapse, and progressive neurodegeneration. Comparative analysis across SCA1, SCA2, SCA3, SCA6, SCA7, DRPLA, and SBMA enables PROJECT STRANDSHIFT to identify shared therapeutic leverage points while preserving disease-specific biological precision.