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MADD
MAP kinase activating death domain
MADD is located on the short (p) arm of chromosome 11, at band 11p11.2. Arm ratio per GRCh38 - banding schematic.
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Overview
MADD (MAP kinase activating death domain) is located on chromosome 11 and encodes a 1647-amino acid protein involved in regulating cellular communication networks. The protein functions as a scaffolding molecule, bringing together different signalling components and coordinating their activity in response to growth factors and other external cues. Research suggests that MADD also participates in membrane trafficking processes, helping to direct proteins to their correct destinations within the cell. Pathogenic variants in MADD have been identified in individuals with neurodevelopmental phenotypes, including intellectual disability and epilepsy, leading to the gene's inclusion on UK clinical diagnostic panels for these conditions.
What the gene does
The MADD protein serves dual roles in cellular biology, acting both as a signalling adaptor and as a regulator of intracellular transport. In the signalling context, MADD interacts with components of the mitogen-activated protein kinase (MAPK) pathway, which transmits signals from cell-surface receptors to the nucleus to influence gene expression and cell behaviour. The protein's death domain enables it to engage with receptor complexes and modulate their downstream effects, potentially influencing cell survival and apoptosis pathways.
In membrane trafficking, MADD belongs to the DENN domain protein family, which regulates the activity of Rab GTPases-molecular switches that control the formation, movement and fusion of membrane-bound vesicles. By modulating Rab protein function, MADD influences how cells sort and transport cargo proteins, maintain organelle identity and respond to nutrient availability. This trafficking function appears particularly important in neurons, where precise protein localisation is essential for synaptic communication and network development. The integration of signalling and trafficking roles suggests that MADD coordinates cellular responses by linking external stimuli to changes in membrane organisation and protein distribution.
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Chromosome location
MADD is positioned on the short arm of chromosome 11 at band p11.2, a region near the centromere. The precise genomic coordinates place the gene in a chromosomal neighbourhood containing other genes involved in developmental and metabolic processes. Structural details regarding the number and organisation of exons encoding the full-length transcript have not been comprehensively characterised in all publicly available databases.
Protein structure
The MADD protein comprises several distinct functional modules organised along its 1647-amino acid sequence. The N-terminal region contains the uDENN domain (amino acids 14-268), followed by the cDENN domain (amino acids 289-429) and the dDENN domain (amino acids 431-565). These three DENN domains together form the characteristic architecture that enables MADD to function as a guanine nucleotide exchange factor for Rab proteins, facilitating membrane trafficking events. The C-terminal portion of the protein features a death domain (amino acids 1340-1415), which mediates protein-protein interactions with signalling receptors and adaptors. Interspersed throughout the sequence are multiple disordered regions (amino acids 108-168, 604-636, 678-842, 913-941, 1051-1110 and 1146-1243), which likely provide structural flexibility and enable the protein to adopt different conformations when binding to various interaction partners. This modular organisation allows MADD to integrate signals from multiple pathways simultaneously.
Key variants
Genetic variation in MADD encompasses a range of sequence changes, including missense substitutions, small insertions and deletions, and potentially larger structural rearrangements. The inheritance pattern is classified as polygenic, indicating that effects on phenotype may involve contributions from variants at multiple genetic loci rather than single Mendelian variants. Variants identified in clinical settings have been associated with neurodevelopmental presentations, though the precise mechanisms by which specific sequence changes alter protein function remain under investigation.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.2344dup | p.Glu782fs | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.2816+1G>A | - | Pathogenic | ★★☆☆ | Deeah syndrome |
c.4594C>T | p.Arg1532Ter | Pathogenic | ★★☆☆ | Neurodevelopmental disorder with dysmorphic facies, impaired speech, and hypotonia |
c.979C>T | p.Arg327Ter | Pathogenic/Likely pathogenic | ★★☆☆ | MADD-related disorder |
c.4080del | p.Lys1361fs | Pathogenic | ★☆☆☆ | MADD-related disorder |
c.4109T>A | p.Leu1370Ter | Pathogenic | ★☆☆☆ | Multiple acyl-CoA dehydrogenase deficiency, severe neonatal type |
c.4286_4287del | p.Ser1429fs | Pathogenic | ★☆☆☆ | Inborn genetic diseases |
c.4392_4395del | p.Cys1464fs | Pathogenic | ★☆☆☆ | Inborn genetic diseases |
c.710C>G | p.Ser237Ter | Pathogenic | ★☆☆☆ | not provided |
c.3637_3638del | p.Asp1212_Ser1213insTer | Pathogenic | - | Neurodevelopmental disorder with dysmorphic facies, impaired speech, and hypotonia |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
MADD variants have been identified in individuals with neurodevelopmental conditions characterised by intellectual disability and epilepsy. These phenotypes likely reflect disruption of the protein's roles in neuronal signalling and membrane trafficking during brain development. The gene's presence on NHS clinical panels for intellectual disability and early-onset epilepsy indicates that MADD testing is considered clinically relevant when evaluating individuals with these presentations. The specific clinical features and their severity may vary depending on the nature and location of the genetic variant, and phenotypic expression may be influenced by other genetic and environmental factors.
No disease links recorded for this gene in our reference set.
UK clinical status
MADD is included on several NHS Genomic Medicine Service panels with green confidence ratings, indicating strong evidence for its clinical validity. The gene appears on the DDG2P (Developmental Disorders Genotype-to-Phenotype) panel, the Early Onset or Syndromic Epilepsy panel (R59) and the Intellectual Disability panel (R29). These panel memberships reflect expert consensus that MADD variants contribute to neurodevelopmental phenotypes and that the gene should be analysed when these clinical features are present. Green ratings signify that there is robust evidence linking MADD to the associated conditions, supporting its use in diagnostic genomic testing within the NHS.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does the MADD gene do?
MADD encodes a protein that regulates cellular signalling pathways and membrane trafficking. It helps coordinate how cells respond to external signals and how proteins are sorted and transported within cells, processes that are particularly important in the developing nervous system.
How is MADD inherited?
MADD is classified as polygenic, meaning that its contribution to disease risk may involve interactions with variants at other genetic loci rather than following a simple Mendelian inheritance pattern. The genetic architecture of MADD-related conditions is still being characterised.
Is MADD testing available on the NHS?
Yes, MADD is included on several NHS Genomic Medicine Service panels, including those for intellectual disability and early-onset epilepsy, with green confidence ratings. This means testing may be available through NHS clinical genetics services when these features are present.