No abstract

The transcription factor BCL11B is essential for development of the nervous and the immune system, and Bcl11b deficiency results in structural brain defects, reduced learning capacity, and impaired immune cell development in mice. However, the precise role of BCL11B in humans is largely unexplored, except for a single patient with a BCL11B missense mutation, affected by multisystem anomalies and profound immune deficiency. Using massively parallel sequencing we identified 13 patients bearing heterozygous germline alterations in BCL11B. Notably, all of them are affected by global developmental delay with speech impairment and intellectual disability; however, none displayed overt clinical signs of immune deficiency. Six frameshift mutations, two nonsense mutations, one missense mutation, and two chromosomal rearrangements resulting in diminished BCL11B expression, arose de novo. A further frameshift mutation was transmitted from a similarly affected mother. Interestingly, the most severely affected patient harbours a missense mutation within a zinc-finger domain of BCL11B, probably affecting the DNA-binding structural interface, similar to the recently published patient. Furthermore, the most C-terminally located premature termination codon mutation fails to rescue the progenitor cell proliferation defect in hippocampal slice cultures from Bcl11b-deficient mice. Concerning the role of BCL11B in the immune system, extensive immune phenotyping of our patients revealed alterations in the T cell compartment and lack of peripheral type 2 innate lymphoid cells (ILC2s), consistent with the findings described in Bcl11b-deficient mice. Unsupervised analysis of 102 T lymphocyte subpopulations showed that the patients clearly cluster apart from healthy children, further supporting the common aetiology of the disorder. Taken together, we show here that mutations leading either to BCL11B haploinsufficiency or to a truncated BCL11B protein clinically cause a non-syndromic neurodevelopmental delay. In addition, we suggest that missense mutations affecting specific sites within zinc-finger domains might result in distinct and more severe clinical outcomes.

The SPAST gene encoding for spastin plays a central role in the genetically heterogeneous group of diseases termed hereditary spastic paraplegia (HSP). In this study, we attempted to expand and refine the genetic and phenotypic characteristics of SPAST associated HSP by examining a large cohort of HSP patients/families. Screening of 200 unrelated HSP cases for mutations in the SPAST gene led to detection of 57 mutations (28.5%), of which 47 were distinct and 29 were novel mutations. The distribution analysis of known SPAST mutations over the structural domains of spastin led to the identification of several regions where the mutations were clustered. Mainly, the clustering was observed in the AAA (ATPases associated with diverse cellular activities) domain; however, significant clustering was also observed in the MIT (microtubule interacting and trafficking), MTBD (microtubule-binding domain) and an N-terminal region (228 -269 residues). Furthermore, we used a previously generated structural model of spastin as a framework to classify the missense mutations in the AAA domain from the HSP patients into different structural/functional groups. Our data also suggest a tentative genotype-phenotype correlation and indicate that the missense mutations could cause an earlier onset of the disease.

Cancer stem cell studies may improve understanding of tumor pathophysiology and identify more effective strategies for cancer treatment. In a variety of organisms, Piwil2 has been implicated in multiple roles including stem cell self-renewal, RNA silencing, and translational control. In this study, we documented specific expression of the stem cell protein Piwil2 in breast cancer with predominant expression in breast cancer stem cells. In patients who were evaluated, we determined that 90% of invasive carcinomas and 81% of carcinomas in situ exhibited highest expression of Piwil2. In breast cancer cells, Piwil2 silencing suppressed the expression of signal transducer and activator of transcription 3, a pivotal regulator of Bcl-X L and cyclin D1, whose downregulation paralleled a reduction in cell proliferation and survival. Our findings define Piwil2 and its effector signaling pathways as key factors in the proliferation and survival of breast cancer stem cells. Cancer Res; 70(11); 4569-79. ©2010 AACR.