Microcephalin (MCPH1) is a gene mutated in primary microcephaly, an autosomal recessive neurodevelopmental disorder in which there is a marked reduction in brain size. PCC syndrome is a recently described disorder of microcephaly, short stature, and misregulated chromosome condensation. Here, we report the finding that MCPH1 primary microcephaly and PCC syndrome are allelic disorders, both having mutations in the MCPH1 gene. The two conditions share a common cellular phenotype of premature chromosome condensation in the early G2 phase of the cell cycle, which, therefore, appears to be a useful diagnostic marker for individuals with MCPH1 gene mutations. We demonstrate that an siRNA-mediated depletion of MCPH1 is sufficient to reproduce this phenotype and also show that MCPH1-deficient cells exhibit delayed decondensation postmitosis. These findings implicate microcephalin as a novel regulator of chromosome condensation and link the apparently disparate fields of neurogenesis and chromosome biology. Further characterization of MCPH1 is thus likely to lead to fundamental insights into both the regulation of chromosome condensation and neurodevelopment.

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Biochemical Society Trdnsactions ( 1 996) 24 2 7 3 s STRSO 2 S T R 4 9 STRJS 2 1 1 1 S T R 4 4 3 SC 1 SG 3 1.1

BackgroundNodal marginal zone B-cell lymphoma is a rare entity in which the cytogenetic findings are not well defined. The t(2;14)(p24;q32) has previously been reported in three patients with blastic mantle cell lymphoma and one patient with follicular lymphoma. This rearrangement has not been reported previously in a patient with a diagnosis of nodal marginal zone B-cell lymphoma.Case presentationWe present a male patient who presented with lymphadenopathy. On the basis of his clinicoradiologic presentation, morphological appearances, immunophenotype and molecular findings he was determined to have a diagnosis of nodal marginal zone B-cell lymphoma. Cytogenetic analysis demonstrated a t(2;14)(p24;q32). Further FISH testing showed this rearrangement to involve the MYCN and IGH genes.ConclusionsWe present the first patient with a diagnosis of nodal marginal zone B-cell lymphoma with a t(2;14)(p24;q32). This rearrangement has been described in three other patients who have had a diagnosis of lymphoma. Our findings suggest this rearrangement is not specific to mantle cell lymphoma or follicular lymphoma. The number of cases described are still too low to draw firm conclusions regarding the nature of this rearrangement. In order to refine the clinical and prognostic picture of this finding, publication of further cases is required.