Tiaira J. Porter

The brain is a high-energy tissue, and although aging is associated with dysfunctional inflammatory and neuron-specific functional pathways, a direct connection to metabolism is not established. Here, we show that isoforms of mitochondrial regulator PGC-1α are driven from distinct brain cell-type specific promotors, repressed with aging, and integral in coordinating metabolism and growth signaling. Transcriptional and proteomic profiles of cortex from male adult, middle age, and advanced age mice reveal an aging metabolic signature linked to PGC-1α. In primary culture, a neuron-exclusive promoter produces the functionally dominant isoform of PGC-1α. Using growth repression as a challenge, we find that PGC-1α is regulated downstream of GSK3β independently across promoters. Broad cellular metabolic consequences of growth inhibition observed in vitro are mirrored in vivo, including activation of PGC-1α directed programs and suppression of aging pathways. These data place PGC-1α centrally in a growth and metabolism network directly relevant to brain aging.

A growing body of research explores the experiences of students in graduate education and more-particularly, students of color pursuing advanced degrees. However, little research provides information about Black students' aspirations to pursue graduate education in science, technology, engineering, and mathematics (STEM). Even less is known about Black males' aspirations to pursue graduate education in STEM. Knowing why Black males aspire to pursue graduate education would assist stakeholders (e.g., administrators, faculty, advisors, family members, and peers) in better supporting and motivating students while they are in graduate school, or earlier in their educational trajectories. This retrospective study of 50 Black males' aspirations for graduate school aimed to better understand the factors that influenced their aspirations to pursue graduate degrees in engineering. Four themes were most influential: (a) Black male students received messages implying that a bachelor's degree was insufficient, (b) earning a graduate degree in engineering was regarded as a sign of community influence and respect, (c) students' professorial career goals necessitated an advanced degree, and (d) mothers functioned as support systems and role models for earning an advanced degree. Finally, we offer implications for future research and practice. These new findings about aspirations regarding graduate education will assist stakeholders in identifying critical moments and experiences necessary to encourage talented individuals to pursue advanced degrees in STEM fields.

The brain is a high energy tissue, and the cell types of which it is comprised are distinct in function and in metabolic requirements. The transcriptional co-activator PGC-1a is a master regulator of mitochondrial function and is highly expressed in the brain; however, its cell-type specific role in regulating metabolism has not been well established. Here, we show that PGC-1a is responsive to aging and that expression of the neuron specific PGC-1a isoform allows for specialization in metabolic adaptation. Transcriptional profiles of the cortex from male mice show an impact of age on immune, inflammatory, and neuronal functional pathways and a highly integrated metabolic response that is associated with decreased expression of PGC-1a. Proteomic analysis confirms age-related changes in metabolism and further shows changes in ribosomal and RNA splicing pathways. We show that neurons express a specialized PGC-1a isoform that becomes active during differentiation from stem cells and is further induced during the maturation of isolated neurons. Neuronal but not astrocyte PGC-1a responds robustly to inhibition of the growth sensitive kinase GSK3b, where the brain specific promoter driven dominant isoform is repressed. The GSK3b inhibitor lithium broadly reprograms metabolism and growth signaling, including significantly lower expression of mitochondrial and ribosomal pathway genes and suppression of growth signaling, which are linked to changes in mitochondrial function and neuronal outgrowth. In vivo, lithium treatment significantly changes the expression of genes involved in cortical growth, endocrine, and circadian pathways. These data place the GSK3b/PGC-1a axis centrally in a growth and metabolism network that is directly relevant to brain aging.

Although exogenous overexpression of a protein fused to a fluorescent tag can provide insight for the protein’s function, it also can produce artifacts attributed to its upregulation and may not fully report the endogenous regulation of the protein of interest. To circumvent these issues, we adapted a protocol to label endogenous proteins with fluorescent tags in primary adult mouse neural stem cells in vitro. Here, we describe reagent construction, reagent delivery, and a screening strategy to isolate edited cells. For complete details on the use and execution of this protocol, please refer to Morrow et al. (2020).