Germline mutations in telomere biology genes cause dyskeratosis congenita (DC), an inherited bone marrow failure and cancer predisposition syndrome. DC is a clinically heterogeneous disorder diagnosed by the triad of dysplastic nails, abnormal skin pigmentation, and oral leukoplakia; Hoyeraal-Hreidarsson syndrome (HH), a clinically severe variant of DC, also includes cerebellar hypoplasia, immunodeficiency, and intrauterine growth retardation. Approximately 70% of DC cases are associated with a germline mutation in one of nine genes, the products of which are all involved in telomere biology. Using exome sequencing, we identified mutations in Adrenocortical Dysplasia Homolog (ACD) (encoding TPP1), a component of the telomeric shelterin complex, in one family affected by HH. The proband inherited a deletion from his father and a missense mutation from his mother, resulting in extremely short telomeres and a severe clinical phenotype. Characterization of the mutations revealed that the single-aminoacid deletion affecting the TEL patch surface of the TPP1 protein significantly compromises both telomerase recruitment and processivity, while the missense mutation in the TIN2-binding region of TPP1 is not as clearly deleterious to TPP1 function. Our results emphasize the critical roles of the TEL patch in proper stem cell function and demonstrate that TPP1 is the second shelterin component (in addition to TIN2) to be implicated in DC.

The shelterin complex plays dual functions in telomere homeostasis by recruiting telomerase and preventing the activation of a DNA damage response at telomeric ends. Somatic stem cells require telomerase activity, as evidenced by progressive stem cell loss leading to bone marrow failure in hereditary dyskeratosis congenita. Recent work demonstrates that dyskeratosis congenita can also arise from mutations in specific shelterin genes, although little is known about shelterin functions in somatic stem cells. We found that mouse hematopoietic stem cells (HSCs) are acutely sensitive to inactivation of the shelterin gene Acd, encoding TPP1. Homozygosity for a hypomorphic acd allele preserved the emergence and expansion of fetal HSCs but led to profoundly defective function in transplantation assays. Upon complete Acd inactivation, HSCs expressed p53 target genes, underwent cell cycle arrest, and were severely depleted within days, leading to hematopoietic failure. TPP1 loss induced increased telomeric fusion events in bone marrow progenitors. However, unlike in epidermal stem cells, p53 deficiency did not rescue TPP1-deficient HSCs, indicating that shelterin dysfunction has unique effects in different stem cell populations. Because the consequences of telomere shortening are progressive and unsynchronized, acute loss of shelterin function represents an attractive alternative for studying telomere crisis in hematopoietic progenitors.

Group B streptococcus (GBS) is one of the leading causes of neonatal infection; however the molecular mechanisms involved are not clearly known. Here we used high and low hemolytic GBS isolates and mutant GBS that lacks β-hemolysin expression and showed that GBS infection or exposure to GBS-hemolysin extract induces primary human trophoblast, placental fibroblast and JEG3 trophoblast cell line death, and that GBS-induced trophoblast death was β-hemolysin dependent. The fibroblasts and trophoblasts provide an innate immune barrier between fetal and maternal circulation in the placenta. These data suggest that GBS may disrupt this barrier to invade fetal circulation.

Septins are highly conserved cytoskeletal GTP-binding proteins implicated in numerous cellular processes from apoptosis to vesicle trafficking. Septins have been associated with leukemia and solid tumor malignancies, including breast, ovarian, and prostate. We previously reported that high SEPT9_i1 expression in human mammary epithelial cell lines (HMECs) led to malignant cellular phenotypes such as increased cell proliferation, invasiveness, motility, and genomic instability. Our goal here was to better understand how SEPT9_i1 expression might contribute to genomic instability and malignant progression. First, we confirmed that even transient expression of SEPT9_i1 was sufficient to increase aneuploidy in HMECs. We then analyzed SEPT9_i1 by immunoprecipitation and immunofluorescence studies and found that SEPT9_i1 interacts with both α and γ tubulin. SEPT9_i1 expressing cells demonstrated dramatic chromosome segregation defects, centrosome amplification and cytokinesis defects, suggesting two possible molecular mechanisms contributing to the development of genomic instability. This suggests that SEPT9_i1 may promote genomic instability through both cytokinesis and mitotic spindle defects which lead to chromosome missegregation.

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Background: Classically protein kinase A (PKA) and transcription factor activator protein 1 (AP-1) mediate the cyclic AMP (cAMP) induced-corticotrophin releasing hormone (CRH) expression in the placenta. However enteric Gram (-) bacterial cell wall component lipopolysaccharide (LPS) may also induce-CRH expression via Toll like receptor (TLR)4 and its adaptor molecule Myd88. Here we investigated the role of MyD88, TRIF and IRAK2 on cAMP-induced CRH promoter activation in JEG3 cells in the absence of LPS/TLR4 stimulation.

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