A loss of function mutation in CLDN25 causing Pelizaeus-Merzbacher-like leukodystrophy.

Area of Science:

• Cell Biology
• Neuroscience
• Genetics

Background:

• Claudin-25 (CLDN-25) is an uncharacterized member of the claudin family with broad tissue expression and less conserved sequences.
• Functional data for CLDN-25, particularly from knockout models, is lacking.
• Claudins are crucial for tight junction integrity and paracellular transport.

Observation:

• A de novo heterozygous missense variant (c.745G>C, p.A249P) in CLDN25 was identified in a patient with Pelizaeus-Merzbacher-like leukodystrophy.
• The CLDN-25 variant protein failed to localize to cell-cell borders.
• The C-terminal end of CLDN-25, independent of ZO-1 binding, is essential for its junctional localization.

Findings:

• The A249P mutant and a C-terminal deletion mutant of CLDN-25 did not localize to cell borders in vitro.
• Cellular CLDN25 knockout increased tight junction integrity but also solute movement between cells.
• The study proposes CLDN-25 acts as a 'decoy' claudin, influencing cell-cell interactions.

Implications:

• The CLDN25 mutation likely causes haploinsufficiency, contributing to leukodystrophy.
• Understanding CLDN-25's function is key to comprehending claudin roles in health and disease.
• Targeting CLDN-25 expression may modulate barrier function in 'leaky' cells.