Fanconi anemia (FA) is a rare genomic instability disorder characterized by progressive bone marrow failure and predisposition to cancer. FA-associated gene products are involved in the repair of DNA interstrand crosslinks (ICLs). Fifteen FA-associated genes have been identified, but the genetic basis in some individuals still remains unresolved. Here, we used whole-exome and Sanger sequencing on DNA of unclassified FA individuals and discovered biallelic germline mutations in ERCC4 (XPF), a structure-specific nuclease-encoding gene previously connected to xeroderma pigmentosum and segmental XFE progeroid syndrome. Genetic reversion and wild-type ERCC4 cDNA complemented the phenotype of the FA cell lines, providing genetic evidence that mutations in ERCC4 cause this FA subtype. Further biochemical and functional analysis demonstrated that the identified FA-causing ERCC4 mutations strongly disrupt the function of XPF in DNA ICL repair without severely compromising nucleotide excision repair. Our data show that depending on the type of ERCC4 mutation and the resulting balance between both DNA repair activities, individuals present with one of the three clinically distinct disorders, highlighting the multifunctional nature of the XPF endonuclease in genome stability and human disease.

To date there is no effective therapy for Alzheimer disease (AD). High levels of circulating high density lipoprotein (HDL) and its main protein, apolipoprotein A-I (apoA-I), reduce the risk of cardiovascular disease. Clinical studies show that plasma HDL cholesterol and apoA-I levels are low in patients with AD. To investigate if increasing plasma apoA-I/HDL levels ameliorates AD-like memory deficits and amyloid-␤ (A␤) deposition, we generated a line of triple transgenic (Tg) mice overexpressing mutant forms of amyloid-␤ precursor protein (APP) and presenilin 1 (PS1) as well as human apoA-I (AI). Here we show that APP/PS1/AI triple Tg mice have a 2-fold increase of plasma HDL cholesterol levels. When tested in the Morris water maze for spatial orientation abilities, whereas APP/PS1 mice develop age-related learning and memory deficits, APP/PS1/AI mice continue to perform normally during aging. Interestingly, no significant differences were found in the total level and deposition of A␤ in the brains of APP/PS1 and APP/PS1/AI mice, but cerebral amyloid angiopathy was reduced in APP/PS1/AI mice. Also, consistent with the anti-inflammatory properties of apoA-I/HDL, glial activation was reduced in the brain of APP/ PS1/AI mice. In addition, A␤-induced production of proinflammatory chemokines/cytokines was decreased in mouse organotypic hippocampal slice cultures expressing human apoA-I. Therefore, we conclude that overexpression of human apoA-I in the circulation prevents learning and memory deficits in APP/ PS1 mice, partly by attenuating neuroinflammation and cerebral amyloid angiopathy. These findings suggest that elevating plasma apoA-I/HDL levels may be an effective approach to preserve cognitive function in patients with AD.

Background: 8-OxoG is a major oxidative lesion in DNA and is associated with cancer. Results: Kinetic and mass spectrometric studies demonstrate that human polymerase bypasses 8-oxoG in a largely error-free manner. Conclusion: Arginine 61 from the finger domain plays a key role in error-free bypass at the insertion stage. Significance: In addition to photo-adducts and cisplatinated DNA, polymerase might also be involved in accurate bypass of 8-oxoG in vivo.

Objective-The majority of apoptotic cells in atherosclerotic lesions are macrophages. However, the pathogenic role of macrophage apoptosis in the development of atherosclerosis remains unclear. Elevated expression of Bax, one of the pivotal proapoptotic proteins of the Bcl-2 family, has been found in human atherosclerotic plaques. Activation of Bax also occurs in free cholesterol-loaded and oxysterol-treated mouse macrophages. In this study, we examined the effect of Bax deficiency in bone marrow-derived leukocytes on the development of atherosclerosis in low-density lipoprotein receptor-null (LDLRϪ/Ϫ) mice. Methods and Results-Fourteen 8-week-old male LDLRϪ/Ϫ mice were lethally irradiated and reconstituted with either wild-type (WT) C57BL6 or Bax-null (BaxϪ/Ϫ) bone marrow. Three weeks later, the mice were challenged with a Western diet for 10 weeks. No differences were found in the plasma cholesterol level between the WT and BaxϪ/Ϫ group. However, quantitation of cross sections from proximal aorta revealed a 49.2% increase (Pϭ0.0259) in the mean lesion area of the BaxϪ/Ϫ group compared with the WT group. A 53% decrease in apoptotic macrophages in the BaxϪ/Ϫ group was found by TUNEL staining (PϽ0.05). Conclusions-The reduction of apoptotic activity in macrophages stimulates atherosclerosis in LDLRϪ/Ϫ mice, which is consistent with the hypothesis that macrophage apoptosis suppresses the development of atherosclerosis.