rs1978060 — TBX1

TBX1 rs1978060 — A Developmental Regulator's Role in Spinal Architecture and Ear Health

TBX1¹¹ TBX1
T-box transcription factor 1, the master regulator of pharyngeal arch development encoded at chromosome 22q11.21 is best known as the gene whose haploinsufficiency causes DiGeorge syndrome²² DiGeorge syndrome
22q11.2 deletion syndrome, characterised by heart defects, immune deficiency from thymic hypoplasia, and palate abnormalities. Rare catastrophic TBX1 deletions displace entire developmental programmes. But common intronic variants like rs1978060 operate more subtly: they modulate how much TBX1 the cell transcribes, shifting developmental outcomes by degrees rather than eliminating them altogether.

The G allele of rs1978060 acts as a cis-expression quantitative trait locus (cis-eQTL) — it reduces TBX1 expression in tissues where TBX1 matters for skeletal and muscular patterning. Among the consequences, the one with the strongest population-level evidence is susceptibility to adolescent idiopathic scoliosis³³ adolescent idiopathic scoliosis
AIS, abnormal lateral spinal curvature appearing during the pubertal growth spurt, affecting ~3% of adolescents worldwide with a strong female predominance.

The Mechanism

TBX1 is expressed in the paraxial mesoderm and the pharyngeal arches during embryogenesis, directing the formation of the pharynx, thymus, parathyroids, aortic arch, and the musculoskeletal components of the cervical and thoracic spine. In post-natal life, residual TBX1 activity influences the maintenance of paraspinal musculature. When TBX1 expression is reduced — as the G allele cis-eQTL effect produces — paraspinal muscle fibres show altered proportions of fibre types, and the resulting asymmetric loading across the growing spine may initiate or accelerate curvature.

Li et al. 2021⁴⁴ Li et al. 2021 confirmed this mechanistic link directly: TBX1 protein was measurably reduced in paraspinal muscle biopsies from AIS patients compared with congenital scoliosis controls, and the degree of reduction correlated with curve magnitude (r = −0.519, p = 0.003). This dose-response relationship between TBX1 expression and curve severity is the clearest molecular evidence that the rs1978060 eQTL effect has functional consequences in living tissue.

TBX1's role in pharyngeal arch development — particularly formation of the Eustachian tube and middle ear structures — also makes it a plausible candidate for ear-infection susceptibility in the general population. The 23andMe multi-infection GWAS (Tian et al. 2017, >200,000 Europeans) identified the TBX1 locus in associations with childhood ear infections and myringotomy, consistent with subtle Eustachian tube geometry or mucosal immune variation downstream of reduced TBX1 expression.

The Evidence

The primary discovery came from Kou et al. 2019⁵⁵ Kou et al. 2019
Genome-wide association study identifies 14 previously unreported susceptibility loci for AIS in Japanese — Nature Communications, a meta-analysis of three GWAS studies comprising 79,211 Japanese individuals. Rs1978060 at Chr22q11.21 reached genome-wide significance (p < 5×10⁻⁸) and was accompanied by cis-eQTL evidence linking the G allele to lower TBX1 expression.

Replication followed in Li et al. 2021⁶⁶ Li et al. 2021
Genetic variant of TBX1 is functionally associated with AIS in the Chinese population — Spine, enrolling 1,725 female AIS patients and 2,600 healthy controls in a Chinese Han cohort. The G allele showed OR 1.12 per allele for AIS susceptibility, consistent with an additive effect. The tissue expression data in this study provides the strongest functional link: TBX1 mRNA was significantly lower in paraspinal muscle of AIS patients, and the correlation with Cobb angle held across the patient cohort.

The effect size (OR ~1.12) places this variant in the category of common variants with modest individual effects — typical for complex developmental traits where dozens of loci collectively shape risk. The G allele frequency of ~61% globally means a large proportion of the population carries at least one copy; population-level burden is therefore meaningful even with a small per-allele OR.

Practical Actions

The variant's primary actionable consequence centres on scoliosis screening during the adolescent growth period. Early detection of scoliosis allows timely bracing, which is effective when started before curve progression. GG carriers — particularly adolescent girls, who are disproportionately affected by AIS — benefit most from awareness and systematic monitoring during the pubertal growth spurt. Note that a 2025 study (Dai et al., PMID 39206768) found rs1978060 does not significantly predict brace treatment outcome, suggesting the variant is most relevant for susceptibility awareness rather than treatment guidance.

For ear health, the TBX1 locus association with otitis media susceptibility observed in the large 23andMe GWAS (Tian et al. 2017) is consistent with a structural basis — Eustachian tube geometry and mucosal immune function — rather than a classical innate immune defect. Persistent or recurrent ear infections in G carriers may warrant audiological assessment and active management rather than watchful waiting.

Interactions

TBX1 lies at the centre of the 22q11.2 deletion region. The rs1978060 eQTL effect represents a common allelic series on the same biological axis as the rare 22q11.2 deletion. Carriers of the G allele do not have DiGeorge syndrome and will have normal thymic output, immune function, and cardiac anatomy — the eQTL effect is quantitative and tissue-limited, not equivalent to haploinsufficiency.

The most plausible interaction for future compound action research would involve other paraspinal development loci identified in the Kou 2019 GWAS (e.g., BNC2, CHD7, SOX9/KCNJ2 loci at rs10738445, rs1017861, rs12946942). Combined burden across multiple AIS susceptibility variants predicts risk better than any single locus, though specific compound action data for this combination are not yet published.