Microcephalin: a causal link between impaired damage response signalling and microcephaly
Mark O'Driscoll1, Andrew P Jackson, Penny A Jeggo
1Genome Damage and Stability Centre, University of Sussex, East Sussex, UK.
Abstract:
Seckel Syndrome (SS) and Primary Microcephaly (MCPH) are disorders exhibiting marked microcephaly with a head circumference less than three standard deviations below the mean. ATR-Seckel Syndrome is conferred by mutations in ataxia and telangiectasia and Rad3 related (ATR), a kinase that activates a DNA damage signalling response. Cell lines from additional SS patients, who are normal for ATR, show defective ATR signalling, suggesting that they carry mutations in other components of the ATR pathway. Primary Microcephaly is distinct from SS since patients display solely microcephaly without accompanying marked growth delay. MCPH1, the first Primary Microcephaly causative gene identified, encodes three BRCT domains, similar to other damage response proteins. Recent studies employing MCPH1 siRNA or exploiting cell lines from MCPH1 patients have shown that MCPH1 functions in the ATR-dependent DNA damage response pathway. Additionally, MCPH1 has a function in the regulation of mitotic entry that is ATR-independent and confers a characteristic phenotype of premature chromosome condensation. Recent studies will be reviewed and their relationship to the aetiology of microcephaly discussed.
Insights
Seckel Syndrome and Primary Microcephaly involve small head size. Mutations in ATR and MCPH1 genes disrupt DNA damage response and cell division, causing these developmental disorders.
Area of Science:
- Genetics
- Molecular Biology
- Developmental Biology
Background:
- Seckel Syndrome (SS) and Primary Microcephaly (MCPH) are characterized by severe microcephaly.
- ATR-Seckel Syndrome is linked to mutations in the ATR kinase, crucial for DNA damage response.
- MCPH1, associated with Primary Microcephaly, also plays a role in DNA damage pathways.
Purpose of the Study:
- To review recent studies on the genetic basis of microcephaly disorders.
- To discuss the roles of ATR and MCPH1 in DNA damage signaling and cell cycle regulation.
- To explore the relationship between these genes and the etiology of microcephaly.
Main Methods:
- Analysis of cell lines from patients with SS and MCPH.
- Investigating mutations in ATR and MCPH1 genes.
- Review of existing literature on DNA damage response pathways and mitotic entry regulation.
Main Results:
- Defective ATR signaling is observed in SS patients without ATR mutations, suggesting involvement of other ATR pathway components.
- MCPH1 functions in the ATR-dependent DNA damage response.
- MCPH1 also regulates mitotic entry independently of ATR, leading to premature chromosome condensation.
Conclusions:
- Mutations in ATR and MCPH1 disrupt critical cellular processes, leading to microcephaly.
- The ATR pathway and MCPH1 are key players in the etiology of Seckel Syndrome and Primary Microcephaly.
- Understanding these pathways offers insights into developmental brain size regulation.
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