SEDLIN Forms Homodimers: Characterisation of SEDLIN Mutations and Their Interactions with Transcription Factors MBP1, PITX1 and SF1
Figure 5
Schematic model for SEDLIN homodimerization and SEDL expression in common cell lines.
(A) Homodimers that have formed between the transfected mutant cMyc-SEDLIN and the endogenously expressed wild-type SEDLIN could mask the loss of interaction between mutant SEDLINs and MBP1, PITX1 and SF1 in transfected COS7 cells. Thus, although the mutant SEDLIN may not directly interact with MBP1, PITX1 or SF1, the endogenously expressed SEDLIN will interact with these transcription factors, and hence the resultant homodimers will overall be seen to interact with the transcription factors. This proposed model provides an explanation for the observed results in the transfected cells. However, it is important to note that this situation of homodimers consisting of a wild-type and mutant SEDLIN would not normally occur in males affected with SEDT, as they are hemizygous and their cells would normally express the mutant SEDLIN; however this situation would occur in SEDT heterozygous carrier females because the SEDL gene escapes X-chromosome inactivation [13] and hence their cells would express both the wild-type and mutant SEDLINs. (B) RT-PCR analysis was used to detect the endogenous expression of SEDL in COS7, COS1, HEK293 and HK2 kidney cells, as a reliable SEDLIN antibody is not available. Detection of Calmodulin expression was used as an internal control for RNA quality and concentration; (+) with RTase, (−) without RTase.