Figure 2. Effect of haploinsufficiency of Nf1 on coat color and total numbers of cutaneous and peritoneal mast cells.

(A) Coat color pattern of a representative mouse from each of the following genotypes: +/+;+/+, Nf1^+/-;+/+, +/+;W⁴¹/W⁴¹, and Nf1^+/-;W⁴¹/W⁴¹. Haploinsufficiency at Nf1partially corrects the coat color deficiency in mice homozygous for the W41 allele in a C57BL/6 genetic background. (B) Representative cytospins from peritoneal lavages stained for mast cells from individual mice of the four Nf1 and W genotypes. Peritoneal cells were stained with toluidine blue to quantify the total number of mast cells per peritoneal lavage. A higher magnification of a representative mast cell is shown in the inset of the wild-type mouse (original magnification: 3200). Bar (inset) 10 μm. Bar (far right) 30 μm. (C) Representative ear biopsies stained for cutaneous mast cells from individual mice of the four Nf1 and W genotypes. Specimens were stained with hematoxylin-eosin to assess routine histology, and with Giemsa to identify mast cells. Ear biopsies were stained with Fontana-Masson to differentiate melanin-containing cells from mast cells. Cutaneous mast cells (Giemsa-positive, Fontana-Masson–negative) were quantitated in a blinded fashion by counting the distal 5 mm of ears. Black arrows indicate Giemsa-positive mast cells, and open arrows indicate Fontana-Masson melanin–containing cells. Bar, 35 μm. © Ingram et al.,2000. Originally published in J. Exp.Med. 191: 181–188.