Focused ultrasound-mediated brain genome editing

Gene editing in the brain has been challenging because of the restricted transport imposed by the blood-brain barrier (BBB). Current approaches mainly rely on local injection to bypass the BBB. However, such administration is highly invasive and not amenable to treating certain delicate regions of the brain. We demonstrate a safe and effective gene editing technique by using focused ultrasound (FUS) to transiently open the BBB for the transport of intravenously delivered CRISPR/Cas9 machinery to the brain.

Efficient in vivo neuronal genome editing in the mouse brain using nanocapsules containing CRISPR-Cas9 ribonucleoproteins

Genome editing of somatic cells via clustered regularly interspaced short palindromic repeats (CRISPR) offers promise for new therapeutics to treat a variety of genetic disorders, including neurological diseases. However, the dense and complex parenchyma of the brain and the post-mitotic state of neurons make efficient genome editing challenging. In vivo delivery systems for CRISPR-Cas proteins and single guide RNA (sgRNA) include both viral vectors and non-viral strategies, each presenting different advantages and disadvantages for clinical application. We developed non-viral and biodegradable PEGylated nanocapsules (NCs) that deliver preassembled Cas9-sgRNA ribonucleoproteins (RNPs). Here, we show that the RNP NCs led to robust genome editing in neurons following intracerebral injection into the healthy mouse striatum. Genome editing was predominantly observed in medium spiny neurons (>80%), with occasional editing in cholinergic, calretinin, and parvalbumin interneurons. Glial activation was minimal and was localized along the needle tract. Our results demonstrate that the RNP NCs are capable of safe and efficient neuronal genome editing in vivo.

Impact of dual diagnosis on healthcare and criminal justice costs after release from Queensland prisons: a prospective cohort study

BACKGROUND

People released from prison have poorer health than the general public, with a particularly high prevalence of mental illness and harmful substance use. High-frequency use of hospital-based services is costly, and greater investment in transitional support and primary care services to improve the health of people leaving prison may therefore be cost-effective.

METHODS

A prospective cohort study of 1303 men and women released from prisons in Queensland, Australia, between 2008 and 2010, using linked data was performed. We calculated healthcare costs and the cost of re-incarceration. We compared healthcare costs to the general public, and assessed the impact of past mental illness, substance use disorder, and dual diagnosis on both healthcare and criminal justice costs.

RESULTS

Healthcare costs among the cohort were 2.1-fold higher than expected based on costs among the public. Dual diagnosis was associated with 3.5-fold higher healthcare costs (95% CI 2.6-4.6) and 2.8-fold higher re-incarceration costs (95% CI 1.6-5.0), compared with no past diagnosis of either mental illness or substance use disorder.

CONCLUSIONS

People released from prison incur high healthcare costs, primarily due to high rates of engagement with emergency health services and hospital admissions. Comorbid mental illness and substance use disorders are associated with high health and criminal justice costs among people recently released from prison.

Activation-induced cytidine deaminase-initiated off-target DNA breaks are detected and resolved during S phase

Activation-induced cytidine deaminase (AID) initiates DNA double-strand breaks (DSBs) in the IgH gene (Igh) to stimulate isotype class switch recombination (CSR), and widespread breaks in non-Igh (off-target) loci throughout the genome. Because the DSBs that initiate class switching occur during the G₁ phase of the cell cycle, and are repaired via end joining, CSR is considered a predominantly G₁ reaction. By contrast, AID-induced non-Igh DSBs are repaired by homologous recombination. Although little is known about the connection between the cell cycle and either induction or resolution of AID-mediated non-Igh DSBs, their repair by homologous recombination implicates post-G₁ phases. Coordination of DNA breakage and repair during the cell cycle is critical to promote normal class switching and prevent genomic instability. To understand how AID-mediated events are regulated through the cell cycle, we have investigated G₁-to-S control in AID-dependent genome-wide DSBs. We find that AID-mediated off-target DSBs, like those induced in the Igh locus, are generated during G₁. These data suggest that AID-mediated DSBs can evade G₁/S checkpoint activation and persist beyond G₁, becoming resolved during S phase. Interestingly, DSB resolution during S phase can promote not only non-Igh break repair, but also Ig CSR. Our results reveal novel cell cycle dynamics in response to AID-initiated DSBs, and suggest that the regulation of the repair of these DSBs through the cell cycle may ensure proper class switching while preventing AID-induced genomic instability.

Nuclear positioning, higher-order folding, and gene expression of Mmu15 sequences are refractory to chromosomal translocation

Nuclear localization influences the expression of certain genes. Chromosomal rearrangements can reposition genes in the nucleus and thus could impact the expression of genes far from chromosomal breakpoints. However, the extent to which chromosomal rearrangements influence nuclear organization and gene expression is poorly understood. We examined mouse progenitor B cell lymphomas with a common translocation, der(12)t(12;15), which fuses a gene-rich region of mouse chromosome 12 (Mmu 12) with a gene-poor region of mouse chromosome 15 (Mmu 15). We found that sequences 2.3 Mb proximal and 2.7 Mb distal to the der(12)t(12;15) breakpoint had different nuclear positions measured relative to the nuclear radius. However, their positions were similar on unrearranged chromosomes in the same tumor cells and normal progenitor B cells. In addition, higher-order chromatin folding marked by three-dimensional gene clustering was not significantly altered for the 7 Mb of Mmu 15 sequence distal to this translocation breakpoint. Translocation also did not correspond to significant changes in gene expression in this region. Thus, any changes to Mmu 15 structure and function imposed by the der(12)t(12;15) translocation are constrained to sequences near (<2.5 Mb) the translocation junction. These data contrast with those of certain other chromosomal rearrangements and suggest that significant changes to Mmu 15 sequence are structurally and functionally tolerated in the tumor cells examined.

Widespread genomic breaks generated by activation-induced cytidine deaminase are prevented by homologous recombination

Activation induced cytidine deaminase (AID) is required for somatic hypermutation and immunoglobulin class switching in activated B cells. Because AID possesses no known target site specificity, there have been efforts to identify non-immunoglobulin AID targets. We show that AID acts promiscuously, generating widespread DNA double strand breaks (DSB), genomic instability and cytotoxicity in B cells with diminished homologous recombination (HR) capability. We demonstrate that the HR factor XRCC2 suppresses AID-induced off-target DSBs, promoting B cell survival. Finally, we suggest that aberrations affecting human chromosome 7q36, including XRCC2, correlate with genomic instability in B cell cancers. Our findings demonstrate that AID has promiscuous genomic DSB-inducing activity, identify HR as a safeguard against off-target AID action, and have implications for genomic instability in B cell cancers.

Complex oncogenic translocations with gene amplification are initiated by specific DNA breaks in lymphocytes

Chromosomal instability is a hallmark of many tumor types. Complex chromosomal rearrangements with associated gene amplification, known as complicons, characterize many hematologic and solid cancers. Whereas chromosomal aberrations, including complicons, are useful diagnostic and prognostic cancer markers, their molecular origins are not known. Although accumulating evidence has implicated DNA double-strand break repair in suppression of oncogenic genome instability, the genomic elements required for chromosome rearrangements, especially complex lesions, have not been elucidated. Using a mouse model of B-lineage lymphoma, characterized by complicon formation involving the immunoglobulin heavy chain (Igh) locus and the c-myc oncogene, we have now investigated the requirement for specific genomic segments as donors for complex rearrangements. We now show that specific DNA double-strand breaks, occurring within a narrow segment of Igh, are necessary to initiate complicon formation. By contrast, neither specific DNA breaks nor the powerful intronic enhancer Emu are required for complicon-independent oncogenesis. This study is the first to delineate mechanisms of complex versus simple instability and the first to identify specific chromosomal elements required for complex chromosomal aberrations. These findings will illuminate genomic cancer susceptibility and risk factors.

Gallium-avid painless thyroiditis in a patient with AIDS

Intense thyroidal Ga-67 accumulation was seen in a man with AIDS imaged for suspected Pneumocystis carinii pneumonia. Concurrent Tc-99m pertechnetate thyroid scanning demonstrated absent trapping, helping establish the diagnosis of painless thyroiditis. Occult hyperthyroidism, and not pulmonary infection, may have been responsible for the patient's original presenting symptoms.

Management of individual tumor syndromes. Medullary thyroid carcinoma and hyperparathyroidism

Significant advances have been made in the understanding of the pathophysiology and the ability to effectively screen for and treat medullary thyroid carcinoma. The parafollicular cells, or C-cells, are the cell of origin for medullary thyroid carcinoma. C-cell hyperplasia is a premalignant disease that progresses rapidly to medullary thyroid carcinoma. C-cells produce calcitonin, which serves as a marker to prospectively screen patients for C-cell disease. One major concern in screening for this disease has been the incidence of false positive results. This problem is addressed in light of new, more stringent criteria for the diagnosis of C-cell hyperplasia. The association of hyperparathyroidism with MEN 2 is discussed with evidence that thyroidectomy of C-cell disease may affect the incidence of parathyroid disease.

Diurnal pattern of plasma growth hormone-binding protein in man

The identification of specific GH-binding proteins (GH-BP) in human plasma, one of which is a fragment of the GH receptor, has added new complexity to the state of GH in the circulation. A major proportion of GH circulates in complexed form, which differs in kinetics and possibly bioactivity from free GH. Little is known about the regulation of the GH-BP, their constancy or variation in plasma, or plasma factors affecting GH binding. Consequently, the temporal pattern of bound and free GH in plasma is also unknown. Knowledge about possible spontaneous variability in GH-BP levels/activity is required for physiological investigations and comparative studies among different populations. To address these issues, we measured GH-binding activity in plasma every hour over a 24-h period in six normal adults (three men and three women). A standardized GH binding assay, employing incubation of plasma with [125I]GH and separation of bound from free GH by gel filtration, was used. GH-BP activity showed no significant diurnal variation in any subject. The average GH-BP activity was similar in all subjects, although statistically significant differences were found between some subjects. No age- or sex-related differences were identified. We conclude that in normal man plasma GH-BP activity is constant throughout the day, thereby implying 1) constancy of binding protein (and possibly GH receptor) concentration, and 2) absence of significant fluctuations in potential binding inhibitors/enhancers in plasma.