Figure 6.—

BEAF mutations cause a disruption of male X polytene chromosome structure. (A) Salivary gland polytene chromosomes prepared from a wild-type male third instar larvae exhibit a normal banding pattern when the DNA is stained with DAPI. One chromosome arm of polytene chromosomes prepared from a BEAF^AB-KO male has lost the banding pattern and appears shorter and broader. Indirect immunostaining with an antibody against MOF shows that it is the X chromosome that appears abnormal. (B) The GFBF transgene rescues the abnormal phenotype of the BEAF^AB-KO male polytene X chromosome. (Top) Chromosomes stained with DAPI and gently spread in 50% glycerol without acid treatment to allow direct visualization of green fluorescent BEAF fusion proteins. (Bottom) Chromosomes that have undergone normal fixation, with the X chromosome identified by indirect immunostaining with an antibody against MOF. (C) Polytene chromosomes prepared from BEAF^A-KO males show a similar X chromosome phenotype, but it is less extreme and more variable. Note that 32B protein can be detected on these chromosomes by indirect immunofluorescence with an antibody against BEAF. The X chromosome is identified by indirect immunostaining with an antibody against MOF.