Promoter Sequence, Expression, and Fine Chromosomal Mapping of the Human Gene (MLP) Encoding the MARCKS-like Protein: Identification of Neighboring and Linked Polymorphic Loci forMLPandMACSand Use in the Evaluation of Human Neural Tube Defects

The MARCKS-like protein (MLP), also known as F52, MacMARCKS, or MARCKS-related protein, is a widely distributed substrate for protein kinase C (PKC). Recent studies using gene disruptionin vivohave demonstrated the importance of both MARCKS and MLP to the development of the central nervous system; specifically, mice lacking either protein exhibit a high frequency of neural tube defects. We isolated a genomic clone for humanMLPand discovered a directly linked polymorphism (MLP1) useful for genetic linkage analysis. TheMLPpromoter was 71% identical over 433 bp to that of the corresponding mouse gene,Mlp,with conservation of many putative transcription factor-binding sites; it was only 36% identical over 433 bp to the promoter of the human gene,MACS,which encodes the MLP homologue MARCKS. This 433-bp fragment drove expression of anMLP-β-galactosidasetransgene in a tissue-specific and developmental expression pattern that was similar to that observed for the endogenous gene, as shown byin situhybridization histochemistry. In contrast toMACS,theMLPandMlppromoters contain a TATA box approximately 40 bp 5′ of the presumed transcription initiation site.MLPwas localized to chromosome 1p34 → 1pter by analysis of human–mouse somatic cell hybrid DNA and to 1p34 by fluorescencein situhybridization. Radiation hybrid mapping ofMLPplaced it between genetic markersD1S511(LOD > 3.0) andWI9232. MACSwas localized to 6q21 betweenD6S266(LOD > 3.0) andAFM268vh5by the same technique. We tested the novelMLP1polymorphism and theMACSflanking markers in a series of 43 Caucasian simplex families in which the affected child had a lumbosacral myelomeningocele. We found no evidence of linkage disequilibrium, suggesting that these loci were not major genes for spina bifida in these families. Nonetheless, the identification of linked and neighboring polymorphisms forMACSandMLPshould permit similar genetic studies in other groups of patients with neural tube defects and other neurodevelopmental abnormalities.