Figure 1.

A, Pedigree. The pedigree shows a family with dominant inheritance of alactogenesis (closed circles). The proband is indicated by the arrow. The prolactin gene (PRL) mutations (c.658C > T) in all the affected women changed arginine amino acid number 220 to a stop codon (p.Arg220Ter). The second allele was not mutated. The squares denote men and the open circles women who are unaffected or of unknown status. B, C-terminal portion of the prolactin protein. The underline indicates the location of the original p.Arg220Ter mutation. A disulfide bond normally forms between the 2 terminal cysteines, indicated in red. The italics indicates the experimental p.Lys218Ter mutation. The rectangular box indicates the α helix structure. The arrows indicate amino acids important for binding the prolactin receptor.