TPH2 and hyperinsulinemic hypoglycemia, familial, 4: Additionally, probability of dysphagia was also identified in Rdh10 mutant mice with cleft palate due to retinoid deficiency, TPH2 knockout (TPH-/-) mice with serotonin (5-hydroxytryptamine [5-HT]) deficiency, and Uch-L1gad/Uch-L3Δ3–7 double homozygous mice used as a neuro-degenerative animal model [45,46,47].