rs1143699 — PTPRS PTPRS C/T (rs1143699)

PTPRS rs1143699 — A Synonymous Variant That Tags Elevated Diabetes Risk in Men

The PTPRS gene encodes receptor protein tyrosine phosphatase sigma (RPTPσ), a cell-surface enzyme that belongs to the LAR subfamily of receptor-type phosphatases. Although expressed broadly across tissues, PTPRS is particularly abundant in adipose tissue and the brain¹¹ particularly abundant in adipose tissue and the brain
GTEx: RPKM 30.9 in fat, 23.8 in brain, two organ systems central to the energy balance disrupted in type 2 diabetes. RPTPσ removes phosphate groups²² phosphate groups
Dephosphorylation: the removal of a phosphate group from a tyrosine residue, generally attenuating a signalling cascade that was activated by tyrosine kinase activity from tyrosine residues on target proteins, acting as a brake on signalling cascades that phosphorylation events have switched on.

rs1143699 sits in exon 34 of PTPRS on chromosome 19 (19p13.3). The gene is transcribed from the minus strand, so the variant appears as G>A on the plus (genomic) strand but as C>T in coding-strand notation — the same convention used in the original discovery paper. The nucleotide change causes no amino acid substitution (Asp1763 → Asp1763, GAC→GAT), making this a synonymous variant³³ synonymous variant
Also called a silent variant: the DNA sequence changes but the protein sequence stays the same. Synonymous variants can still alter disease risk if they affect mRNA splicing, stability, or local codon usage that changes translation efficiency. The variant most likely acts as a haplotype tag — travelling on the same chromosomal segment as one or more functional changes elsewhere in the gene that alter RPTPσ expression level or activity.

The Mechanism

RPTPσ participates in glucose homeostasis at two levels. In pancreatic beta cells⁴⁴ beta cells
The insulin-secreting cells of the islets of Langerhans in the pancreas; their capacity to release insulin in response to a glucose load is central to preventing type 2 diabetes, it dephosphorylates proteins that regulate insulin granule exocytosis, reducing the efficiency of glucose-induced insulin secretion. In peripheral tissues such as muscle and fat, RPTPσ acts on insulin receptor pathway components, attenuating the insulin signal. The Goto-Kakizaki diabetic rat model⁵⁵ Goto-Kakizaki diabetic rat model
A spontaneously diabetic rat strain used to study T2D mechanisms; GK rats develop non-obese T2D through impaired insulin secretion and peripheral insulin resistance shows approximately 60% overexpression of PTP sigma in islets and liver compared with normoglycaemic controls. When that overexpression was pharmacologically suppressed with antisense oligonucleotides, glucose-induced insulin secretion recovered to near-normal levels, establishing a causal chain between elevated PTPRS activity and impaired beta-cell function.

Conversely, mice lacking PTPRS entirely display reduced fasting plasma glucose and insulin concentrations, together with enhanced whole-body insulin sensitivity, consistent with the idea that higher phosphatase activity suppresses insulin action and epigenetic studies⁶⁶ epigenetic studies
DNA methylation analysis of islets from mice before the onset of diabetes rank PTPRS among the best predictors of future T2D (area under ROC curve 0.62–0.73).

The Evidence

The only published human genetic study of rs1143699 is a Swedish Caucasian case-control cohort⁷⁷ Swedish Caucasian case-control cohort
Långberg et al. 2007, European Journal of Endocrinology — 497 NGT controls, 262 with impaired glucose tolerance, 298 with T2D (n=1,057 total). Three PTPRS variants were tested; rs1143699 was associated with T2D with an overall OR of 1.57 (p=0.029). Stratifying by sex, C/C homozygosity (GG on plus strand is wild-type; A/A on plus strand equals C/C in coding notation and is the risk genotype) conferred a substantially higher odds ratio of 2.19 (p=0.035) in men, with a weaker and non-significant association in women. The sex difference is unexplained but may reflect statistical power limitations in a cohort that was not pre-powered for sex-stratified analysis; both the original Swedish population studied and the limited replication record mean the evidence is best classified as moderate. The A allele frequency is approximately 10-11% in Europeans (gnomAD NFE), making AA homozygotes rare (~1%).

Practical Actions

For the small fraction of individuals who are AA homozygous (approximately 1% of Europeans), the core concern is that elevated RPTPσ activity may blunt both pancreatic insulin secretion and peripheral insulin sensitivity. Interventions that reduce the functional burden on beta cells — such as minimising glycaemic load, prioritising metabolic biomarker monitoring, and reducing adiposity through diet quality rather than generic calorie restriction — may be disproportionately useful. Because the variant is sex-specific in its strongest signal, men with the AA genotype have the most actionable risk profile.

Heterozygous AG carriers have a modest intermediate risk per the dose-response implied by the data. Standard cardiometabolic monitoring remains appropriate.

Interactions

PTPRS harbours two additional variants associated with T2D in the same Swedish cohort: rs4807015 (intronic, OR=1.74 in both sexes) and rs1978237 (intronic, OR=1.59 in both sexes). All three may tag the same haplotype block; their effects may not be additive. The relationship between these three variants in terms of haplotype structure and independence has not been formally assessed in a published follow-up study.