Why this finding matters

Bardet-Biedl syndrome (BBS) is one of the more common syndromic forms of retinitis pigmentosa, a group of inherited retinal disorders in which the retina’s rod and cone photoreceptor cells gradually die. For people and families affected by BBS, identifying the underlying genetic change can be an important part of understanding why the condition occurs within a family and of building a more complete picture of the syndrome’s genetic diversity.

A 2026 study in Ophthalmic Genetics reports a previously unreported change in the MKKS gene in an Afghan family living in Iran. The finding adds to the known range of disease-associated variants in BBS and is especially meaningful because it comes from an understudied population. Broadening representation in genetic research is essential: a genetic change identified in one population may be absent from databases that are built mainly from studies of other groups.

The key finding: a new homozygous MKKS variant

Researchers studied an Afghan patient from a consanguineous family living in Iran. The patient and her two brothers had Bardet-Biedl syndrome. Using whole-exome sequencing—a method that examines the protein-coding portions of many genes at once—the team identified a new variant in MKKS, one of more than 24 genes reported in the development of BBS.

The variant was described as NM_170784.3(MKKS): c.882A>C; p.(Gln294His). This notation provides two complementary pieces of information:

  • c.882A>C means that, in the gene’s coding DNA sequence, the usual DNA letter A was replaced by C at position 882.
  • p.(Gln294His) means that this DNA change is predicted to replace the amino acid glutamine with histidine at position 294 of the MKKS protein.

The variant was homozygous, meaning the affected individual had the same variant in both copies of the MKKS gene. Importantly, it also segregated with the disease phenotype in the family pedigree. In other words, the researchers observed that the variant tracked with BBS in the family members assessed, supporting its relevance to the condition.

Looking beyond the DNA sequence

Finding a genetic change is an important first step, but researchers also need to ask how that change might affect the protein made by the gene. The study therefore used bioinformatics and structural modeling to examine the potential impact of the glutamine-to-histidine substitution.

The team first predicted a three-dimensional model of the MKKS protein and evaluated the quality of that model. They then introduced the newly identified variant into the predicted structure and compared it with the wild-type, or usual, protein model.

Their analysis did not suggest that the variant causes major changes to the protein’s overall three-dimensional shape. However, it did point to a possible local structural effect around amino acid 294. This distinction matters. A protein can retain its broad overall form while a small alteration in one region affects its stability, interactions, or activity. The study therefore provides a structural clue about how the variant may contribute to disease, while also showing why the consequences of individual variants can be subtle and complex.

What this could mean for diagnosis and treatment research

This publication does not test a treatment or establish a new therapy for Bardet-Biedl syndrome. Its immediate value lies in genetic knowledge. Adding the p.(Gln294His) change to the MKKS variant spectrum can help make future genetic interpretation more informed, particularly when this variant—or a similar one—is encountered in families with BBS.

For families undergoing genetic investigation, whole-exome sequencing can be a powerful approach because BBS involves many genes. Identifying a disease-associated variant may help clarify the molecular basis of a family’s condition and can support more precise genetic evaluation within a pedigree.

For researchers, detailed variant reports are foundational for future therapeutic work. Treatment development depends on understanding which genes are involved, what types of variants occur, and how those variants may affect the proteins they encode. Structural analyses, such as the one used in this study, can help generate hypotheses about the functional consequences that future laboratory studies may explore.

Expanding an international BBS research landscape

The newly reported MKKS variant underscores an important principle in inherited retinal disease research: the genetic landscape of BBS is still being mapped. Each carefully characterized family can contribute information that improves the field’s understanding of the syndrome.

By documenting a novel homozygous MKKS variant in an Afghan family living in Iran, this study expands genetic knowledge beyond populations that have historically received more research attention. Continued family-based sequencing, careful assessment of how variants track with disease, and studies of their effects on proteins will be important next steps. Together, this work can strengthen genetic diagnosis and provide a more inclusive foundation for future research into Bardet-Biedl syndrome.