Two novel mutations in the POU1F1 gene generate null alleles through different mechanisms leading to combined pituitary hormone deficiency.
BACKGROUND
Mutations in the POU1F1 gene severely affect the development and function of the anterior pituitary gland and lead to combined pituitary hormone deficiency (CPHD).


OBJECTIVE
The clinical and genetic analysis of a patient presenting with CPHD and functional characterization of identified mutations.


METHODS
We describe a male patient with extreme short stature, learning difficulties, anterior pituitary hypoplasia, secondary hypothyroidism and undetectable prolactin, growth hormone (GH) and insulin-like growth factor 1 (IGF1), with normal random cortisol.


METHODS
The POU1F1 coding region was amplified by PCR and sequenced; the functional consequence of the mutations was analysed by cell transfection and in vitro assays.


RESULTS
Genetic analysis revealed compound heterozygosity for two novel putative loss of function mutations in POU1F1: a transition at position +3 of intron 1 [IVS1+3nt(A>G)] and a point mutation in exon 6 resulting in a substitution of arginine by tryptophan (R265W). Functional analysis revealed that IVS1+3nt(A>G) results in a reduction in the correctly spliced POU1F1 mRNA, which could be corrected by mutations of the +4, +5 and +6 nucleotides. Analysis of POU1F1(R265W) revealed complete loss of function resulting from severely reduced protein stability.


CONCLUSIONS
Combined pituitary hormone deficiency in this patient is caused by loss of POU1F1 function by two novel mechanisms, namely aberrant splicing (IVS1+3nt (A>G) and protein instability (R265W). Identification of the genetic basis of CPHD enabled the cessation of hydrocortisone therapy without the need for further assessment for evolving endocrinopathy.
Division of Molecular Neuroendocrinology, National Institute for Medical Research, The Ridgeway, Mill Hill, London, UK.
J P
JP
Turton
M
M
Strom
S
S
Langham
M T
MT
Dattani
P
P
Le Tissier
D001483:Base Sequence; D015153:Blotting, Western; D002648:Child; D003409:Congenital Hypothyroidism; D004252:DNA Mutational Analysis; D005260:Female; D057809:HEK293 Cells; D019382:Human Growth Hormone / Q000172:deficiency; D006801:Humans; D007018:Hypopituitarism / Q000235:genetics*; D007037:Hypothyroidism / Q000235:genetics; D008297:Male; D009154:Mutation; D010375:Pedigree; D010907:Pituitary Hormones / Q000172:deficiency*; D011388:Prolactin / Q000172:deficiency; D013972:Thyrotropin / Q000172:deficiency / Q000235:genetics; D050817:Transcription Factor Pit-1 / Q000235:genetics* / Q000378:metabolism
C494187:POU1F1 protein, human; D010907:Pituitary Hormones; D050817:Transcription Factor Pit-1; D019382:Human Growth Hormone; D011388:Prolactin; D013972:Thyrotropin