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SAT-039 GNAS-miRNAs Are Likely Involved in the Phenotype of Patients with Pseudohypoparathyroidism 1B/iPPSD3
Ist Teil von
Journal of the Endocrine Society, 2019-04, Vol.3 (Supplement_1)
Ort / Verlag
Washington, DC: Endocrine Society
Erscheinungsjahr
2019
Quelle
Free E-Journal (出版社公開部分のみ)
Beschreibungen/Notizen
Pseudohypoparathyroidism 1B (PHP1B) or inactivating PTH/PTHrp Signaling Disorder type 3 (iPPSD3), according to the new classification, presents mainly with hypocalcemia and hyperphosphatemia due to renal resistance towards parathyroid hormone. In addition, patients display early onset obesity and impaired pubertal growth. The disease is due to a methylation defect at one or several Differentially Methylated Regions (DMR) of the
GNAS
locus, subjected to parental imprinting. 80% of iPPSD3 patients have methylation defect at
GNAS A/B
:TSS-DMR and at least one other
GNAS
DMR (most commonly including
GNAS-AS1
:TSS-DMR). They are known as sporadic cases.
GNAS-miRNAs
are located on the 3'UTR of the antisense transcript
GNAS-AS1
. We hypothesize that abnormal expression of the
GNAS-miRNAs
may contribute to the phenotype of iPPSD3 patients with methylation defect at
GNAS-AS1
:TSS-DMR. We used fibroblasts obtained from a patient with uniparental maternal disomy of chr. 20 (matUPD20) and leukocytes from a patient with paternal UPD20 (patUPD20) and from controls to measure expression of
GNAS-miRNAs
.
In silico
targets of
GNAS-miRNAs
have been characterized using miRbase. Finally, HEK cells were transfected with
GNAS-miRNAs
in order to identify targets. We found that
GNAS-miRNAs
are subjected to parental imprinting. In fact, hsa-miR-296-5p and hsa-miR-296-3p are under-expressed by 400-fold (p=0.0015) and 3.5-fold (p=0.0289) in the fibroblasts of the matUPD20 patient, respectively. We identified
in silico
, three groups of
GNAS-miRNAs
targets classified into cAMP signaling, calcium signaling and growth. Overexpression of hsa-miR-296-3p in HEK cells significantly represses
PRKAG1
and
GNB2
transcripts expression, p<0.001. Overexpression of hsa-miR-298-5p significantly increased transcripts
AKAP6
and
PRKAB2
expression, p<0.001. Overexpression of hsa-miR-296-5p significantly represses
GNB2
transcript expression, p<0.001. In addition, the
GNAS-miRNAs
target
GNAS-AS1
,
A/B
and
Gs
α
the
GNAS
transcripts. In summary, the
GNAS-miRNAs
are subjected to parental imprinting. They likely regulate
in cis
the
GNAS
transcripts and
in
trans
the expression of transcripts involved in the cAMP/PKA (
GNB2
and
AKAP6
) and in the AMPK (
PRKAG1
and
PRKAB2
) pathways, respectively.
PKA
and
AMPK
are involved in lipolysis, fatty acid oxidation and obesity. Therefore, disturbances within AMPK and PKA pathways may explain the early onset obesity phenotype seen in PHP1B patients.