An international research team has identified a genetic defect linking congenital hearing loss with altered pigmentation, shedding new light on the cellular mechanisms underlying inherited deafness. The study focused on a rare condition observed in an extended Palestinian family, where four children across three sets of cousins exhibited moderate bilateral hearing loss accompanied by silvery-gray hair, despite otherwise good health.
The collaborative project, involving scientists from Bethlehem University, the University of Washington, and Tel Aviv University (TAU), pinpointed a variant in the FMN1 gene as the cause. FMN1 encodes Formin-1, a protein critical for maintaining the microscopic structure of the cochlea—the inner ear’s sensory organ responsible for hearing.
Genomic analysis revealed the affected children carried two copies of a rare FMN1 mutation leading to loss of Formin-1 protein function. While other formin protein defects have been linked to various disorders, this marks the first time a human condition has been directly connected to FMN1 mutations.
To investigate how the mutation impairs hearing, researchers studied a pre-existing mouse model lacking functional Formin-1. These mice exhibited similar progressive hearing loss and structural cochlear abnormalities beginning soon after birth, including reduced auditory nerve activity and diminished nerve fiber density. The findings demonstrate that Formin-1 supports a cellular network of protein fibers necessary for the shape, stability, and material transport within the cochlea’s sensory epithelium.
In addition to its role in hearing, Formin-1 is part of a molecular complex involved in melanosome transport, organelles responsible for pigmentation in hair and skin. This dual function may explain the co-occurrence of hearing loss and altered hair color in affected individuals.
“This discovery adds FMN1 to the expanding list of over 200 genes essential for hearing and highlights the significance of supporting cells in cochlear structure, not just sensory hair cells and neurons,” said Prof. Karen B. Avraham of TAU, the study’s senior author. She emphasized the potential for future gene therapy approaches targeting such genetic defects and the importance of identifying clinical markers like pigmentation changes to assist diagnosis.
The research underscores the importance of global scientific cooperation, with contributors bringing decades of collective experience. The work builds on long-standing collaborations involving Prof. Moien Kanaan at Bethlehem University and Prof. Mary-Claire King at the University of Washington, among others. King—renowned for discovering the BRCA1 gene linked to hereditary breast cancer—highlighted how persistence across international and political divides can yield meaningful scientific advances.
The team noted that the FMN1 gene has not previously been included in genetic testing panels for hearing loss, suggesting cases may have been overlooked globally. Improved awareness and genetic screening could lead to earlier diagnosis and treatment options. The group also referenced decreasing rates of consanguinity in Palestinian populations, partly due to increased education and awareness, which may reduce the incidence of recessive genetic disorders in future generations.