Mothers against decapentaplegic homolog 9

Mothers against decapentaplegic homolog 9
SMAD family member 9
External IDs OMIM603295 MGI1859993 HomoloGene21198 GeneCards: SMAD9 Gene
Species Human Mouse
Entrez 4093 55994
Ensembl ENSG00000120693 ENSMUSG00000027796
UniProt O15198 Q9JIW5
RefSeq (mRNA) NM_001127217.2 NM_019483.4
RefSeq (protein) NP_001120689.1 NP_062356.3
Location (UCSC) Chr 13:
37.42 – 37.49 Mb
Chr 3:
54.56 – 54.61 Mb
PubMed search [1] [2]

Mothers against decapentaplegic homolog 9 also known as SMAD9, SMAD8, and MADH6 is a protein that in humans is enocoded by the SMAD9 gene.[1]

SMAD9, as its name describes, is a homolog of the Drosophila gene: "Mothers against decapentaplegic". It belongs to the SMAD family of proteins, which belong to the TGFβ superfamily of modulators. Like many other TGFβ family members, SMAD9 is involved in cell signalling. When a bone morphogenetic protein binds to a receptor (BMP type 1 receptor kinase) it causes SMAD9 to interact with SMAD anchor for receptor activation (SARA).The binding of ligands causes the phosphorylation of the SMAD9 protein and the dissociation from SARA and the association with SMAD4. It is subsequently transferred to the nucleus where it forms complexes with other proteins and acts as a transcription factor. SMAD9 is a receptor regulated SMAD (R-SMAD) and is activated by bone morphogenetic protein type 1 receptor kinase. There are two isoforms of the protein. Confusingly, it is also sometimes referred to as SMAD8 in the literature.


The SMAD proteins are homologs of both the drosophila protein, mothers against decapentaplegic (MAD) and the C. elegans protein SMA. The name is a combination of the two. During Drosophila research, it was found that a mutation in the gene, MAD, in the mother, repressed the gene, decapentaplegic, in the embryo. The phrase "Mothers against" was added since mothers often form organizations opposing various issues e.g. Mothers Against Drunk Driving or (MADD).


  1. ^ Watanabe TK, Suzuki M, Omori Y, Hishigaki H, Horie M, Kanemoto N, Fujiwara T, Nakamura Y, Takahashi E (June 1997). "Cloning and characterization of a novel member of the human Mad gene family (MADH6)". Genomics 42 (3): 446–51. doi:10.1006/geno.1997.4753. PMID 9205116. 

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