Peer support in adolescents and young adults with chronic or rare conditions in northern America and Europe: Targeted literature review.

PROBLEM: Adolescents and young adults with chronic or rare conditions face unique risks to their physical, social and emotional development. Research suggests that peer support improves their quality of life and reduces social isolation. However, there is a paucity of current information considering multiple intervention formats. ELIGIBILITY CRITERIA: A targeted literature review was conducted to identify peer support interventions and assess their feasibility, acceptability and efficacy for this population. Searches were conducted in MEDLINE, Embase and American Psychological Association PsycINFO for records reporting peer support interventions in young adults with chronic or rare conditions. Data were extracted from relevant publications and qualitatively evaluated. SAMPLE: Thirty studies were included, which assessed the use of peer support for young adults (aged 13-30 years) with chronic or rare conditions in Europe or North America. RESULTS: Peer support interventions had positive effects on social positivity, psychosocial development and medical outcomes, though significance was not always demonstrated. CONCLUSIONS: Peer support can enhance care for young adults with chronic or rare conditions. Current literature suggests that once-weekly virtual interventions are the most feasible and acceptable for patients, leading to multifaceted improvements in their well-being. IMPLICATIONS: This study is one of the first to discuss in-person, virtual and hybrid peer-based interventions for young adults with chronic and rare conditions. While all formats improved social, psychological and medical outcomes, virtual formats may be most accessible to participants. Interventions should be made available to this population, and guidelines for optimal implementation of peer support are needed.

TMEM106B deficiency impairs cerebellar myelination and synaptic integrity with Purkinje cell loss.

TMEM106B, a type II lysosomal transmembrane protein, has recently been associated with brain aging, hypomyelinating leukodystrophy, frontotemporal lobar degeneration (FTLD) and several other brain disorders. TMEM106B is critical for proper lysosomal function and TMEM106B deficiency leads to myelination defects, FTLD related pathology, and motor coordination deficits in mice. However, the physiological and pathological functions of TMEM106B in the brain are still not well understood. In this study, we investigate the role of TMEM106B in the cerebellum, dysfunction of which has been associated with FTLD and other brain disorders. We found that TMEM106B is ubiquitously expressed in neurons in the cerebellum, with the highest levels in the Purkinje neurons. Aged TMEM106B-deficient mice show significant loss of Purkinje neurons specifically in the anterior lobe of the cerebellum. Increased microglia and astrocyte activation, as well as an accumulation of ubiquitinated proteins, p62 and TDP-43 were also detected in the cerebellum of aged TMEM106B deficient mice. In the young mice, myelination defects and a significant loss of synapses between Purkinje and deep cerebellar nuclei neurons were observed. Interestingly, TMEM106B deficiency causes distinct lysosomal phenotypes in different types of neurons and glia in the cerebellum and frontal cortex. In humans, TMEM106B rs1990622 risk allele (T/T) is associated with increased Purkinje neuron loss. Taken together, our studies support that TMEM106B regulates lysosomal function in a cell-type-specific manner and TMEM106B is critical for maintaining synaptic integrity and neural functions in the cerebellum.

Loss of TMEM106B and PGRN leads to severe lysosomal abnormalities and neurodegeneration in mice.

Haploinsufficiency of progranulin (PGRN) is a leading cause of frontotemporal lobar degeneration (FTLD). Loss of PGRN leads to lysosome dysfunction during aging. TMEM106B, a gene encoding a lysosomal membrane protein, is the main risk factor for FTLD with PGRN haploinsufficiency. But how TMEM106B affects FTLD disease progression remains to be determined. Here, we report that TMEM106B deficiency in mice leads to accumulation of lysosome vacuoles at the distal end of the axon initial segment in motor neurons and the development of FTLD-related pathology during aging. Ablation of both PGRN and TMEM106B in mice results in severe neuronal loss and glial activation in the spinal cord, retina, and brain. Enlarged lysosomes are frequently found in both microglia and astrocytes. Loss of both PGRN and TMEM106B results in an increased accumulation of lysosomal vacuoles in the axon initial segment of motor neurons and enhances the manifestation of FTLD phenotypes with a much earlier onset. These results provide novel insights into the role of TMEM106B in the lysosome, in brain aging, and in FTLD pathogenesis.

A role of the frontotemporal lobar degeneration risk factor TMEM106B in myelination.

TMEM106B encodes a lysosomal membrane protein and was initially identified as a risk factor for frontotemporal lobar degeneration. Recently, a dominant D252N mutation in TMEM106B was shown to cause hypomyelinating leukodystrophy. However, how TMEM106B regulates myelination is still unclear. Here we show that TMEM106B is expressed and localized to the lysosome compartment in oligodendrocytes. TMEM106B deficiency in mice results in myelination defects with a significant reduction of protein levels of proteolipid protein (PLP) and myelin oligodendrocyte glycoprotein (MOG), the membrane proteins found in the myelin sheath. The levels of many lysosome proteins are significantly decreased in the TMEM106B-deficient Oli-neu oligodendroglial precursor cell line. TMEM106B physically interacts with the lysosomal protease cathepsin D and is required to maintain proper cathepsin D levels in oligodendrocytes. Furthermore, we found that TMEM106B deficiency results in lysosome clustering in the perinuclear region and a decrease in lysosome exocytosis and cell surface PLP levels. Moreover, we found that the D252N mutation abolished lysosome enlargement and lysosome acidification induced by wild-type TMEM106B overexpression. Instead, it stimulates lysosome clustering near the nucleus as seen in TMEM106B-deficient cells. Our results support that TMEM106B regulates myelination through modulation of lysosome function in oligodendrocytes.