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Diploid human cells contain two non-identical genomes, and differences in their regulation underlie human development and disease. We present Fiber-seq Inferred Regulatory Elements (FIRE) and show that FIRE provides a more comprehensive and quantitative snapshot of the accessible chromatin landscape across the 6 Gbp diploid human genome, overcoming previously unrecognized biases in existing regulatory element catalogs. FIRE enables comprehensive detection of haplotype-selective chromatin accessibility (HSCA), exposing novel imprinted elements lacking underlying parent-of-origin CpG methylation differences, and gene regulatory modules that permit genes to escape X chromosome inactivation. We uncover that the human leukocyte antigen (HLA) locus harbors the most HSCA in immune cells, where we resolve specific transcription factor (TF) binding events disrupted by disease-associated variants. Finally, we demonstrate that the regulatory landscape of a cell is littered with autosomal somatic chromatin epimutations that are propagated by clonal expansions to create mitotically stable and non-genetically deterministic chromatin alterations.

Alzheimer’s disease (AD) is a neurodegenerative disease associated with human aging. Ten percent of individuals over 65 years have AD and its prevalence continues to rise with increasing age. There are currently no effective disease modifying treatments for AD, resulting in increasingly large socioeconomic and personal costs. Increasing age is associated with an increase in low-grade chronic inflammation (inflammaging) that may contribute to the neurodegenerative process in AD. Although the exact mechanisms remain unclear, aberrant elevation of reactive oxygen and nitrogen species (RONS) levels from several endogenous and exogenous processes in the brain may not only affect cell signaling, but also trigger cellular senescence, inflammation, and pyroptosis. Moreover, a compromised immune privilege of the brain that allows the infiltration of peripheral immune cells and infectious agents may play a role. Additionally, meta-inflammation as well as gut microbiota dysbiosis may drive the neuroinflammatory process. Considering that inflammatory/immune pathways are dysregulated in parallel with cognitive dysfunction in AD, elucidating the relationship between the central nervous system and the immune system may facilitate the development of a safe and effective therapy for AD. We discuss some current ideas on processes in inflammaging that appear to drive the neurodegenerative process in AD and summarize details on a few immunomodulatory strategies being developed to selectively target the detrimental aspects of neuroinflammation without affecting defense mechanisms against pathogens and tissue damage.

AbstractGlycosylation is a critical post/peri‐translational modification required for the appropriate development and function of the immune system. As an example, abnormalities in glycosylation can cause antibody deficiency and reduced lymphocyte signaling, although the phenotype can be complex given the diverse roles of glycosylation. Human MGAT2 encodes N‐acetylglucosaminyltransferase II, which is a critical enzyme in the processing of oligomannose to complex N‐glycans. Complex N‐glycans are essential for immune system functionality, but only one individual with MGAT2‐CDG has been described to have an abnormal immunologic evaluation. MGAT2‐CDG (CDG‐IIa) is a congenital disorder of glycosylation (CDG) associated with profound global developmental disability, hypotonia, early onset epilepsy, and other multisystem manifestations. Here, we report a 4‐year old female with MGAT2‐CDG due to a novel homozygous pathogenic variant in MGAT2, a 4‐base pair deletion, c.1006_1009delGACA. In addition to clinical features previously described in MGAT2‐CDG, she experienced episodic asystole, persistent hypogammaglobulinemia, and defective ex vivo mitogen and antigen proliferative responses, but intact specific vaccine antibody titers. Her infection history has been mild despite the testing abnormalities. We compare this patient to the 15 previously reported patients in the literature, thus expanding both the genotypic and phenotypic spectrum for MGAT2‐CDG.

1087 Background: OlympiAD (NCT02000622) demonstrated the benefit of olaparib over standard of care in patients (pts) with HER2-negative (HER2-) metastatic breast cancer (MBC) and germline BRCA mutations (gBRCAm). LUCY (NCT03286842) aimed to provide additional data on the real-world effectiveness and safety of olaparib monotherapy in this setting. Methods: This Phase IIIb, open-label, single-arm study of olaparib 300 mg twice-daily, enrolled pts with HER2- gBRCAm MBC who had received a taxane and/or anthracycline in the (neo)adjuvant/metastatic setting, and ≤2 lines of chemotherapy for MBC. Hormone receptor-positive (HR+) pts had progressed on prior endocrine therapy (ET), and further ET was considered unsuitable. Primary endpoint: investigator-defined progression-free survival (PFS). Secondary endpoints: overall survival, time to first subsequent therapy or death (TFST), and investigator-assessed clinical response rate (CRR). The interim analysis was planned after 160 PFS events. Results: From Oct 2018-Sept 2019, 252 pts were enrolled (160 sites, 15 countries; mean age 46.2 [range 22-75] years; 73.4% ECOG PS 0). Median total treatment duration: 7.9 months (mo; range 0.2-20.0). Median PFS: 8.1 mo (95% confidence interval [CI] 6.9, 8.7; 166 events [65.9%]). Clinical trial information: NCT03286842 . Median TFST: 9.7 mo (95% CI 8.7, 11.1). CRR: 48.6% (95% CI 42.2, 55.0). Adverse events (AEs) in >20% of pts (all grades): nausea, anemia, asthenia, vomiting, and fatigue. 24.6% of pts reported a grade ≥3 AE, including anemia (n=33 [13.1%]). 4.4% of pts had an AE leading to treatment discontinuation. Conclusions: Interim results in this real-world population of pts with HER2- gBRCAm MBC were consistent with the OlympiAD study, and support olaparib as a chemotherapy-free alternative treatment for pts with gBRCAm advanced BC. [Table: see text]

The hereditary spastic paraplegias (HSPs) are a heterogeneous group of disorders characterized by degeneration of the corticospinal and spinocerebellar tracts leading to progressive spasticity. One subtype, spastic paraplegia type 47 (SPG47 or HSP‐AP4B1), is due to bi‐allelic loss‐of‐function mutations in the AP4B1 gene. AP4B1 is a subunit of the adapter protein complex 4 (AP‐4), a heterotetrameric protein complex that regulates the transport of membrane proteins. Since 2011, 11 individuals from six families with AP4B1 mutations have been reported, nine of whom had homozygous mutations and were from consanguineous families. Here we report eight patients with AP4B1‐associated SPG47, the majority born to non‐consanguineous parents and carrying compound heterozygous mutations. Core clinical features in this cohort and previously published patients include neonatal hypotonia that progresses to spasticity, early onset developmental delay with prominent motor delay and severely impaired or absent speech development, episodes of stereotypic laughter, seizures including frequent febrile seizures, thinning of the corpus callosum, and delayed myelination/white matter loss. Given that some of the features of AP‐4 deficiency overlap with those of cerebral palsy, and the discovery of the disorder in non‐consanguineous populations, we believe that AP‐4 deficiency may be more common than previously appreciated.

Key Points Low-count and high-count monoclonal B-cell lymphocytosis (MBL) have distinct immunogenetic signatures, with only the latter resembling CLL. Rather than a true premalignant condition, low-count MBL may merely reflect immune senescence or result from persistent antigen stimulation.