ORF01-01 - The Central Nervous System Actions of the Extra-Large Gα -Subunit, XLαs, Are Required for Neonatal Growth, Feeding, and Glycemic Control.

Background: Postnatal metabolic adaptation requires rapid central nervous system (CNS)-mediated coordination of feeding behavior and glucose homeostasis. The GNAS locus encodes multiple products, including XLαs, a paternally expressed variant of the stimulatory G protein α-subunit. Loss of XLαs in humans, such as some patients with Silver-Russell syndrome, is associated with perinatal growth restriction, feeding difficulties, and neonatal hypoglycemia. A similar phenotype is observed in mice with global paternal deletion of Gnasxl. Although XLαs is highly expressed in the neonatal brain, including multiple hypothalamic and brainstem nuclei, and several non-CNS tissues, its tissue-specific contributions remain unclear. We hypothesized that CNS-specific loss of XLαs is sufficient to recapitulate the perinatal findings associated with global XLαs deficiency.

Methods: A conditional Gnasxl allele was generated and used to produce mice with paternal CNS-specific deletion of XLαs (patGnasxlNesKO) using Nestin-Cre. Nestin-Cre littermates lacking the floxed allele served as controls. Recombination efficiency was assessed by deletion-specific PCR. Postnatal day 0 (P0) analyses were performed on mutant and control littermates.

Results: Efficient recombination of the Gnasxl allele was found in the brain of patGnasxlNesKO pups, with minimal recombination in some peripheral tissues. Genotype frequencies at P0 were skewed, with 13 mutants and 23 controls identified in 6 litters, but did not deviate significantly from Mendelian expectations (p = 0.3412). The patGnasxlNesKO offspring were discernible due to their lack of milk spots and small body size, indicating impaired initiation of feeding. Mutant neonates had significantly lower body weight (1318.3 ± 51.93 vs 1417.0 ± 136.2 mg, p = 0.004), reduced stomach weight (6.94 ± 1.13 vs 12.35 ± 6.76 mg, p = 0.001), and stomach-to-body weight ratio (0.0053 ± 0.0002 vs 0.0086 ± 0.0009, p = 0.001). They were also found to have hypoglycemia (28.77 ± 3.223 vs 44.91 ± 2.413 mg/dL, p = 0.0003). All patGnasxlNesKO pups died within 24 hours of birth, whereas no lethality was observed in controls.

Discussion: CNS-specific loss of XLαs is sufficient to reproduce the perinatal growth restriction, feeding failure, hypoglycemia, and neonatal lethality observed in global Gnasxl deficiency. These findings identify XLαs-dependent signaling within the CNS as a critical regulator of early postnatal metabolic adaptation, providing mechanistic insights into endocrine and neuroendocrine pathways underlying neonatal hypoglycemia and feeding disorders.