Heterozygous LHX3 mutations may lead to a mild phenotype of combined pituitary hormone deficiency

Abstract

LHX3 is an LIM domain transcription factor involved in the early steps of pituitary ontogenesis. We report here functional studies of three allelic variants, including the first heterozygous variant of LHX3 NM_178138.5(LHX3):c.587T>C (p. (Leu196Pro)) that may be responsible for a milder phenotype of hypopituitarism. Our functional studies showed that NM_178138.5(LHX3):c.587T>C (p.(Leu196Pro)) was not able to activate target promoters in vitro, as it did not bind DNA, and likely affected LHX3 function via a mechanism of haplo-insufficiency. Our study demonstrates the possibility that patients with a heterozygous variant of LHX3 may have pituitary deficiencies, with a milder phenotype than patients with homozygous variants. It is thus of vital to propose an optimal follow-up of such patients, who, until now, were considered as not being at risk of presenting pituitary deficiency. The second variant NM_178138.5(LHX3):c.622C>G (p.(Arg208Gly)), present in a homozygous state, displayed decreased transactivating ability without loss of binding capacity in vitro, concordant with in silico analysis; it should thus be considered to affect LHX3 function. In contrast, the NM_178138.5 (LHX3):c.929G>C (p.(Arg310Pro)) variant, in a heterozygous state, also predicted as deleterious in silico, proved functionally active in vitro, and should thus still be classified as a variant of unknown significance. Our study emphasizes the need for functional studies due to the limits of software-based predictions of new variants, and the possible association of a pituitary phenotype to heterozygous LHX3 variants.

Clinical lessons learned in constitutional hypopituitarism from two decades of experience in a large international cohort

“…Three mutations of LHX3 were found. Two of them were recently published, with in vitro analysis, by our team 16 . The first one was a girl born to consanguineous parents from Iran presenting with neonatal CPHD, corpus callosum agenesis and retinal dystrophy; she harboured homozygous p.Arg208Gly mutation and both asymptomatic parents showed heterozygous status for this mutation.…”

Rathke’s cleft-like cysts arise from Isl1 deletion in murine pituitary progenitors

“…We used immunostaining to assess expression of pituitary transcription factors and hormones. LHX3 is an essential transcription factor for expansion of Rathke's pouch and most pituitary hormoneproducing cells in mice and humans (62,63). LHX3 immunostaining was normal in the Isl1 Prop1KO mutants at E12.5, indicating commitment to pituitary fate and normal establishment of a dorsal-to-ventral gradient of LHX3 expression (Supplemental Figure 3, A and B).…”

Genetic causes of hypopituitarism

“…Other abnormalities include cervical vertebral malformations (rigid neck, scoliosis), mild developmental delay and moderate sensorineural hearing loss [20]. Heterozygous LHX3 mutations may lead to a mild phenotype of combined pituitary hormone deficiency [21]. Sonic hedgehog (SHH) is an essential morphogenetic signal which dictates cell fate decision in several organs in mammals.…”