Date of Degree
PhD (Doctor of Philosophy)
Bassuk, Alexander G
First Committee Member
Ferguson, Polly J
Second Committee Member
Darbro, Benjamin W
Third Committee Member
Fourth Committee Member
Chronic recurrent multifocal osteomyelitis (CRMO) is a rare, pediatric, autoinflammatory disease characterized by bone pain due to sterile osteomyelitis, and is often accompanied by psoriasis or inflammatory bowel disease. There are two syndromic forms of CRMO, Majeed syndrome and DIRA, for which the genetic cause is known. However, for the majority of cases, the genetic basis is unknown. Via whole-exome sequencing and linkage analysis, we determined the most likely causative mutations in four families. While the mutations are in three different genes – FBLIM1, PLCG2 and PIP; all three genes are involved in Fcγ signaling and osteoclast activation.
In a large cohort of 61 individuals with CRMO, we performed gene and pathway based association analysis using the 1000 genomes participants of European ancestry as controls. One gene from the family-based analyses, ANO6, was significantly enriched for rare variants in our cohort of cases. ANO6 is involved in P2RX7- mediated inflammasome activation and in the regulation of bone mineralization. While no pathways were enriched for rare variants in the CRMO cohort after genome-wide correction, four pathways were significantly enriched for rare variants in the control samples, indicating a protective effect of the variants. The second most significant pathway, activation of chaperone genes by XBP1s, is relevant to CRMO pathogenesis as XBP1s is a transcription factor that attenuates ER stress, and regulates the expression of genes involved in RANKL signaling and bone remodeling.
An association analysis using a larger set of cases followed by functional validation of candidate genes is necessary to confidently declare the mutations isolated in the work presented here to be pathogenic. Our preliminary findings suggest that mutations in genes involved in both the inflammatory response and bone remodeling underlie the pathogenesis of CRMO.
Chronic recurrent multifocal osteomyelitis (CRMO) is a disorder of chronic inflammation that affects the bones of young children. Children with CRMO experience bone pain that is usually worse at night and have elevated markers of inflammation in their blood. They are usually diagnosed and treated by a pediatric rheumatologist. Successful treatment depends on the individual, with some children responding well to NSAIDs or corticosteroids, while others require treatment with IL-1 or TNF-α inhibitors in order for symptoms to improve.
Nearly half of CRMO patients have a strong family history of either psoriasis or inflammatory bowel disease (Ulcerative Colitis or Crohn Disease), suggesting that CRMO is genetic. In the work presented here, CRMO patients and their family members were sequenced in order to determine which genes are involved in the development of CRMO. Three genes that have not been previously linked to disease were isolated, as well as the gene PLCG2, which is known to be mutated in a disease related to CRMO. All four genes are involved in inflammation and the maintenance of bone mineral density. Our results verify that there is a large genetic component to the development of CRMO and highlight new cellular processes that may be targeted in the treatment of CRMO, as well as psoriasis or inflammatory bowel disease.
bone, inflammation, whole exome sequencing
x, 132 pages
Includes bibliographical references (pages 119-132).
Copyright © 2016 Allison Jeanne Cox
Cox, Allison Jeanne. "Whole exome analysis of individuals and families with chronic recurrent multifocal osteomyelitis (CRMO)." PhD (Doctor of Philosophy) thesis, University of Iowa, 2016.