Purinergic receptors P2RX4 and P2RX7 in familial multiple sclerosis
A Dessa Sadovnick1,2, Ben J Gu3, Anthony L Traboulsee2
1Department of Medical Genetics, University of British Columbia, Vancouver, Canada.
Abstract:
Genetic variants in the purinergic receptors P2RX4 and P2RX7 have been shown to affect susceptibility to multiple sclerosis (MS). In this study, we set out to evaluate whether rare coding variants of major effect could also be identified in these purinergic receptors. Sequencing analysis of P2RX4 and P2RX7 in 193 MS patients and 100 controls led to the identification of a rare three variant haplotype (P2RX7 rs140915863:C>T [p.T205M], P2RX7 rs201921967:A>G [p.N361S], and P2RX4 rs765866317:G>A [p.G135S]) segregating with disease in a multi-incident family with six family members diagnosed with MS (logarithm of odds = 3.07). Functional analysis of this haplotype in HEK293 cells revealed impaired P2X7 surface expression (P < 0.01), resulting in over 95% inhibition of adenosine triphosphate (ATP)-induced pore function (P < 0.001) and a marked reduction in phagocytic ability (P < 0.05). In addition, transfected cells showed 40% increased peak ATP-induced inward current (P < 0.01), and a greater Ca2+ response to the P2X4 135S variant compared with wild type (P < 0.0001). Our study nominates rare genetic variants in P2RX4 and P2RX7 as major genetic contributors to disease, further supporting a role for these purinergic receptors in MS and the disruption of transmembrane cation channels leading to impairment of phagocytosis as the pathological mechanisms of disease.
Insights
Rare genetic variants in purinergic receptors P2RX4 and P2RX7 significantly impact multiple sclerosis (MS) risk. These variants disrupt cell function, impairing phagocytosis and supporting a role for purinergic signaling in MS pathogenesis.
Area of Science:
- Neuroimmunology
- Genetics
- Cell Biology
Background:
- Genetic variations in purinergic receptors P2RX4 and P2RX7 are linked to multiple sclerosis (MS) susceptibility.
- The role of rare, high-impact coding variants in these receptors remains to be fully elucidated.
Purpose of the Study:
- To investigate the presence and functional impact of rare coding variants in P2RX4 and P2RX7 associated with MS.
- To determine if these variants contribute significantly to MS pathogenesis through disruption of purinergic signaling pathways.
Main Methods:
- Sequencing of P2RX4 and P2RX7 in 193 MS patients and 100 controls.
- Identification and segregation analysis of a rare haplotype in a multi-incident MS family.
- In vitro functional assays using HEK293 cells to assess P2X7 surface expression, ATP-induced pore function, phagocytosis, and calcium signaling.
Main Results:
- A rare three-variant haplotype (P2RX7 rs140915863:C>T [p.T205M], P2RX7 rs201921967:A>G [p.N361S], and P2RX4 rs765866317:G>A [p.G135S]) was identified, segregating with MS in a family.
- Functional analysis revealed impaired P2X7 surface expression, >95% inhibition of ATP-induced pore function, and reduced phagocytic ability.
- Transfected cells exhibited increased ATP-induced inward current and enhanced Ca2+ response to the P2X4 135S variant.
Conclusions:
- Rare genetic variants in P2RX4 and P2RX7 act as major genetic contributors to MS.
- Disruption of transmembrane cation channels and impaired phagocytosis are proposed pathological mechanisms.
- These findings reinforce the critical role of purinergic receptors in MS pathogenesis.
