Mutations in pericentrin cause Seckel syndrome with defective ATR-dependent DNA damage signaling

Abstract

Expansion of the brain is one of the defining characteristics of modern humans. Seckel syndrome (MIM210600), a disorder of markedly reduced brain and body size1,2, is associated with defective ATR-dependant DNA damage signalling3. Previously, only a single hypomorphic mutation of ATR has been identified in this genetically heterogeneous condition4. We now report that mutations in pericentrin (PCNT) also cause Seckel syndrome, resulting in its loss from the centrosome, where it has key functions anchoring both structural and regulatory proteins5,6. Furthermore, we find that PCNT-Seckel patient cells have defects in ATR-dependent checkpoint signalling, providing the first evidence linking a structural centrosomal protein with DNA damage signalling. These findings also suggest that other known microcephaly genes implicated in either DNA repair responses7 or centrosomal function8,9, may act in common developmental pathways determining human brain and body size.

Promoter hijack reveals pericentrin functions in mitosis and the DNA damage response

“…We next examined the role of pericentrin in the DNA damage response. 23,29 Current models suggest that pericentrin interacts with Mcph1 and thus affects Chk1 signaling to Cdk1. 29,36 To explore this idea, we tested the genetic interactions between Pcnt and Mcph1 by targeting Mcph1 in our Pcnt Δ/Δ cells using a previously published strategy.…”

“…We have not observed the increase in centrosome number in the absence of DNA damage that was described in PCNT mutant human lymphoblastoid cell lines. 23 However, this may be a technical issue. As we noted in our description of Mcph1-deficient DT40 cells, 32 where we also did not detect centrosome amplification that had been described in MCPH1 mutant patient cells, 41 the analysis in human cells was performed after extended…”

“…Loss-of-function mutations in PCNT have been described in microcephalic osteodysplastic primordial dwarfism type II (MOPD II; MIM 210720), a rare condition that is characterized by extremely short stature and microcephaly, but without marked mental retardation. 22 PCNT mutations have also been described in SCKL patients, 23 although the clinical features of PCNT-SCKL patients could fit with an MOPD II diagnosis. 24 Importantly, cells from PCNT-SCKL patients also show defective RT-PCR (Fig.…”

“…We saw no impact of pericentrin deficiency on centrosome composition, as determined by fluorescence microscopy DNA damage responses. 23 One key cell cycle regulatory step that occurs at the centrosome is the activation of Cdk1-cyclin B at the onset of mitosis. 25 It has been reported that centrosomal Chk1 regulates this activation through its inhibition of the Cdk1-activating Cdc25B phosphatase.…”

An ATM- and ATR-dependent checkpoint inactivates spindle assembly by targeting CEP63

“…Centrosome structural protein pericentrin could be part of this G2/M arrest pathway, as suggested from the identification pericentrin mutations causing Seckel-syndrome (Griffith et al, 2008). Although the function of pericentrin in this checkpoint mechanism has not been established, it was posited that either pericentrin could aid Chk1 recruitment to centrosomes or alternatively assist in downstream signalling to centrosome components involved in the arrest.…”