Unrestrained ESCRT-III drives micronuclear catastrophe and chromosome fragmentation.

The ESCRT-III membrane fission machinery maintains the integrity of the nuclear envelope. Although primary nuclei resealing takes minutes, micronuclear envelope ruptures seem to be irreversible. Instead, micronuclear ruptures result in catastrophic membrane collapse and are associated with chromosome fragmentation and chromothripsis, complex chromosome rearrangements thought to be a major driving force in cancer development. Here we use a combination of live microscopy and electron tomography, as well as computer simulations, to uncover the mechanism underlying micronuclear collapse. We show that, due to their small size, micronuclei inherently lack the capacity of primary nuclei to restrict the accumulation of CHMP7-LEMD2, a compartmentalization sensor that detects loss of nuclear integrity. This causes unrestrained ESCRT-III accumulation, which drives extensive membrane deformation, DNA damage and chromosome fragmentation. Thus, the nuclear-integrity surveillance machinery is a double-edged sword, as its sensitivity ensures rapid repair at primary nuclei while causing unrestrained activity at ruptured micronuclei, with catastrophic consequences for genome stability.

Possible link between FSH and RANKL release from adipocytes in men with impaired gonadal function including Klinefelter syndrome.

INTRODUCTION: The FSH receptor (FSHR) has been found to be expressed in human bone cells and bone marrow-adipocytes, and highly-debated mouse studies have suggested extra-gonadal effects of gonadotropins on glucose, adipocyte and bone homeostasis. These putative effects could be direct or indirectly mediated by endocrine factors released from bone-cells or adipocytes. Here, we investigated whether gonadotropins are linked with glucose- and lipid-metabolism in hypergonadotropic men. METHODS: Single centre, cross-sectional study of 307 men with idiopathic infertility and 28 men with Klinefelter syndrome (KS). OUTCOME: associations between serum LH and FSH with soluble-RANKL (sRANKL), osteoprotegerin (OPG), osteocalcin, fasting glucose and insulin, sex steroids, and body composition. Expression of FSHR was studied in human-derived adipocyte-cell-models (hMADS, TERT-hWA) and FSH stimulation of RANKL expression and secretion in hMADS in vitro. RESULTS: Serum FSH was not directly linked with glucose- and lipid-metabolism. However, FSH was inversely associated with sRANKL in both infertile men and KS men (p = .023 and p = .012). Infertile men with elevated FSH (>11 U/L) had significantly lower sRANKL (p = .015). sRANKL was positively associated with fat percentage, fasting insulin, and glucose (all p < .05). Men with prediabetes had higher sRANKL (p = .021), but lower testosterone (p < .0001) and Inhibin B (p = .005). The FSHR was expressed in the investigated human derived adipocytes, and 3-6 h treatment with FSH markedly increased RANKL release (p < .05). CONCLUSION: KS and infertile men with prediabetes have low Inhibin B, and testosterone but elevated RANKL compared with non-prediabetic men despite comparable levels of serum gonadotropins. Serum FSH and sRANKL was inversely associated in both infertile and KS men, but the increased release of RANKL from FSH treated adipocytes suggest a direct effect of FSH on RANKL production in some tissues. Further studies are required to clarify whether FSH targets RANKL in the skeleton. ClinicalTrial_ID:NCT01304927.

Characterization of immortalized human brown and white pre-adipocyte cell models from a single donor.

Brown adipose tissue with its constituent brown adipocytes is a promising therapeutic target in metabolic disorders due to its ability to dissipate energy and improve systemic insulin sensitivity and glucose homeostasis. The molecular control of brown adipocyte differentiation and function has been extensively studied in mice, but relatively little is known about such regulatory mechanisms in humans, which in part is due to lack of human brown adipose tissue derived cell models. Here, we used retrovirus-mediated overexpression to stably integrate human telomerase reverse transcriptase (TERT) into stromal-vascular cell fractions from deep and superficial human neck adipose tissue biopsies from the same donor. The brown and white pre-adipocyte cell models (TERT-hBA and TERT-hWA, respectively) displayed a stable proliferation rate and differentiation until at least passage 20. Mature TERT-hBA adipocytes expressed higher levels of thermogenic marker genes and displayed a higher maximal respiratory capacity than mature TERT-hWA adipocytes. TERT-hBA adipocytes were UCP1-positive and responded to ß-adrenergic stimulation by activating the PKA-MKK3/6-p38 MAPK signaling module and increasing thermogenic gene expression and oxygen consumption. Mature TERT-hWA adipocytes underwent efficient rosiglitazone-induced 'browning', as demonstrated by strongly increased expression of UCP1 and other brown adipocyte-enriched genes. In summary, the TERT-hBA and TERT-hWA cell models represent useful tools to obtain a better understanding of the molecular control of human brown and white adipocyte differentiation and function as well as of browning of human white adipocytes.