Transcription factor SOX-2
positive regulation of DNA-templated transcription
Novel mutations in LHX3 are associated with hypopituitarism and sensorineural hearing loss.
Homozygous loss-of-function mutations in the transcription factor LHX3 have been associated with hypopituitarism with structural anterior pituitary defects and cervical abnormalities with or without restricted neck rotation. We report two novel recessive mutations in LHX3 in four patients from two unrelated pedigrees. Clinical evaluation revealed that all four patients exhibit varying degrees of bilateral sensorineural hearing loss, which has not been previously reported in association with LHX3 mutations, in addition to hypopituitarism including adrenocorticotropic hormone deficiency and an unusual skin and skeletal phenotype in one family. Furthermore, re-evaluation of three patients previously described with LHX3 mutations showed they also exhibit varying degrees of bilateral sensorineural hearing loss. We have investigated a possible role for LHX3 in inner ear development in humans using in situ hybridization of human embryonic and fetal tissue. LHX3 is expressed in defined regions of the sensory epithelium of the developing inner ear in a pattern overlapping that of SOX2, which precedes the onset of LHX3 expression and is known to be required for inner ear and pituitary development in both mice and humans. Moreover, we show that SOX2 is capable of binding to and activating transcription of the LHX3 proximal promoter in vitro. This study therefore extends the phenotypic spectrum associated with LHX3 mutations to encompass variable sensorineural hearing loss and suggests a possible interaction between LHX3 and SOX2 likely to be important for development of both the inner ear and the anterior pituitary in human embryonic development.