Molecular and clinical evaluation of a patient hemizygous for TIGR/MYOC

Abstract

Objective: To determine if a patient with an interstitial deletion of chromosome 1 is hemizygous for the TIGR/MYOC gene and if that patient has glaucoma.

Methods: A patient with an interstitial deletion of chromosome 1 was clinically examined for evidence of glaucoma. DNA samples from the patient and her family were used for molecular studies to determine the boundaries of the chromosome 1 deletion using polymorphic markers located on chromosome 1q21 to 1q24. Additional markers located in the vicinity of the TIGR/MYOC gene, including 2 derived from the ends of the gene, were used to determine if it was included in the deletion.

Results: The patient and her family showed no evidence of glaucoma. Molecular analysis demonstrated that a complex deletion of the maternal copy of chromosome 1 included the entire TIGR/MYOC gene.

Conclusions: We have determined that the patient has only 1 functional copy of TIGR/MYOC. The lack of clinical evidence of glaucoma suggests that haploinsufficiency of the TIGR/MYOC protein is not the cause of early-onset glaucoma associated with mutations in TIGR/MYOC.

Clinical relevance: Missense and nonsense mutations in the TIGR/MYOC gene have been associated with juvenile- and adult-onset primary open-angle glaucoma. Although many different mutations have been correlated with the disease, the underlying genetic mechanism (haploinsufficiency, gain of function, or a dominant negative effect) remains unknown. Information regarding the genetic mechanism responsible for TIGR/MYOC-associated glaucoma is necessary for further studies designed to develop transgenic animal models and gene-related therapy.