Figure 3. Isl1 is required for gonadotrope and thyrotrope lineages.

(A–D) FOXL2 and CGA immunostaining in control (A, n = 3; C, n = 4) and Isl1^Prop1KO (B, n = 3; D, n = 4) pituitary glands at E13.5. (E and F) TSH immunostaining in control (n = 3) and Isl1^Prop1KO (n = 7) pituitary glands at E16.5.(G and H) NR5A1 immunostaining in E16.5 control (n = 3) and Isl1^Prop1KO (n = 3) pituitaries. (I and J) Gata2 ISH in E16.5 pituitaries of control (n = 7) and Isl1^Prop1KO (n = 8). (K–N) LH and TSH immunostaining in P3 pituitaries in controls (n = 3) and Isl1^Prop1KO (n = 3). (O and P) Quantitation of LH and TSH immunopositive cells per unit area of the pituitary at P0 reveals decreases in gonadotropes (control, n = 5, range = 5.4–14.9; Isl1^Prop1KO, n = 4, range = 1.5–7.1) and thyrotropes (control, n = 5, range = 26.7–43.4; Isl1^Prop1KO, n = 4, range = 12.1–20.5) in Isl1^Prop1KO. (Q–T) E18.5 control and tamoxifen-induced ablation of ISL1 (CAG-Cre-ERT2;Isl1^fl/fl) mouse model were immunostained for FSH (control, n = 3; mutant, n = 3) and TSH (control, n = 5; mutant, n = 5). Arrows indicate rare gonadotropes in both types of ISL1-deficient mutants. (U and V) Quantitation of FSH- and TSH-positive cells per unit area revealed decreases in both cell populations in CAG-Cre-ERT2;Isl1^fl/fl mutants (FSH, range = 0.14–0.2; TSH, range = 0.2–0.7) relative to controls (FSH, range = 0.8–2.0; TSH, range = 1.3–3.1). (W) Male and female Isl1^Prop1KO mice (male, n = 8, range = 6.2–12.6 g; female, n = 11, range = 5.2–13.8g) weigh less than control littermates (male, n = 10, range = 10.5–14.7 g; female, n = 12, range = 10.8–17.7 g) at 3 weeks and have reduced serum T4 (X, control, n = 7, range = 0.94–3.18; mutant, n = 7, range = 0.0–2.33). Scale bars: 50 μm (A–L, N, O, Q–U). Sagittal orientation (A–F, I, J, Q–U), coronal orientation (G, H, K–O). Statistical significance was determined using Student’s t test, 1-tail distribution, 2-sample equal variance (O, P, and U–X). *P < 0.05; **P < 0.01; ***P < 0.001.