Genotype–Laterality Associations in DNAAF11-Related Primary Ciliary Dyskinesia: Functional Characterization of the p.Ile100Thr Variant
This study characterizes the DNAAF11 p.Ile100Thr variant as causing reduced protein abundance and reviews a cohort of patients to demonstrate that recurrent DNAAF11 variants are associated with variable laterality phenotypes, precluding the establishment of specific variant-situs associations.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Inside the human body, microscopic hair-like structures called cilia line the airways and sweep away mucus and dust, keeping the lungs clear. These same tiny hairs play a critical role very early in life, when an embryo is just beginning to form. At that stage, cilia in a specific spot create a gentle, directional flow that tells the developing body which side is left and which is right. When these cilia do not work correctly, two major problems can arise: the airways become vulnerable to chronic infection and damage, and the internal organs may end up on the wrong side of the body, a condition known as situs inversus totalis. This collection of symptoms is called primary ciliary dyskinesia. While scientists have identified dozens of genes that can cause this disorder, the precise impact of many specific genetic changes remains unclear, leaving doctors and families without a complete picture of what a particular mutation means for a patient's health.
A team of researchers at Shanghai General Hospital recently focused on one such genetic change to see if it truly causes the disease and how it affects the body's development. They studied a woman in her thirties who had lived with a chronic cough and bronchiectasis, a condition where the airways are permanently widened and damaged, for over twenty years. Unusually, she also had situs inversus totalis, meaning her heart and other major organs were mirrored on the opposite side of her chest and abdomen. By examining her DNA and that of her parents, the researchers found that she had inherited two copies of a specific change in a gene called DNAAF11. This gene provides instructions for making a protein that helps assemble the motor parts of the cilia. The woman's parents each carried one copy of the change but were healthy, which fits the pattern of a recessive genetic disorder where two copies are needed to cause illness.
To understand what this specific change, known as p.Ile100Thr, actually does, the scientists moved from the patient to the laboratory. They created two versions of the DNAAF11 gene: one that matched the healthy human version and one that carried the patient's mutation. They inserted these genes into human cells grown in a dish and watched how the cells behaved. The results showed that while the cells with the mutated gene produced the correct amount of genetic instructions, or mRNA, they made significantly less of the final protein. It is as if the factory received the blueprints but struggled to build the actual machinery. This drop in protein levels suggests that the mutation disrupts the stability of the protein or how the cell handles it, which would prevent the cilia from assembling correctly. The researchers also used computer modeling to look at the shape of the protein. They found that the mutation swaps one building block for another at a specific spot, creating new chemical bonds that likely alter the protein's structure and make it less stable.
The team then looked beyond this single patient to see if this same genetic change appeared in others and what it meant for them. They reviewed medical records for sixty-three patients worldwide who had mutations in the DNAAF11 gene. Among the fifty-one patients for whom they had information about organ placement, twenty-nine had some form of laterality defect, such as having their organs mirrored or arranged in a mixed pattern. The specific mutation the researchers studied was found in three different patients in total: the woman from Shanghai, an Italian patient, and another patient from China. All three had respiratory symptoms and issues with organ placement. However, the study also revealed that other patients with the same mutation did not necessarily have the exact same symptoms, and some people with different mutations had similar outcomes. This indicates that while the mutation is harmful, it does not guarantee a single specific outcome for every person who carries it.
The researchers concluded that the p.Ile100Thr mutation is likely a cause of primary ciliary dyskinesia, supported by the fact that it reduces the amount of functional protein in cells and appears in patients with the classic disease symptoms. However, they emphasized that the link between this specific genetic change and the exact pattern of organ placement is not absolute. The variation seen among patients suggests that other factors, perhaps other genes or environmental influences, also play a role in determining whether an individual develops situs inversus or a different arrangement of organs. While the study provides strong evidence that this mutation is harmful, it also highlights the complexity of the disease, showing that even when the same genetic error occurs, the body's response can vary. Further work using cells that naturally grow cilia will be needed to fully understand how this mutation stops the tiny hairs from working and to clarify the full range of effects it has on human development.
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