Transcriptional control and the regulation of endocrine genes

Feline hyperthyroidism: advances towards novel molecular therapeutics

Feline hyperthyroidism is the most common endocrine disorder of the elderly cat. Traditionally, the disease is treated by surgical thyroidectomy, medical management with antithyroid drugs or radiation therapy using iodine-131. However, none of these treatments is ideal and molecular therapeutics may offer novel methods of treating the disease. This article reviews the background of, and preliminary investigations into, the development of a transcriptionally targeted somatic gene therapy strategy for the treatment of this feline condition.

Characterization of the feline thyroglobulin promoter

The feline thyroglobulin promoter was identified by a combination of standard polymerase chain reaction (PCR) techniques, using primers designed according to regions of homology in published sequences from other species, then adaptor ligated PCR. A 310 bp fragment of the feline thyroglobulin promoter was generated, including 8 nucleotides of adaptor sequence at the 5' end and, based on the putative transcription start site, 36 nucleotides of the thyroglobulin mRNA (untranslated portion). The homology between the feline promoter sequence (from 193 bp upstream to the putative cap site) and canine, bovine and human sequences was 89%, 81% and 78%, respectively. Transient transfection studies, using reporter constructs in which the feline promoter controlled expression of chloramphenicol acetyl transferase, demonstrated promoter activity in thyroid cells, but no activity in non-thyroid cells. The data presented here demonstrate that the feline thyroglobulin promoter may provide a targeting mechanism for somatic gene therapy of feline thyroid disease.