New articles on neurodegenerative diseases from Prof. Weidong Le, our Editor-in-Chief

Our staff editors continue to share exciting, interesting, and thought-provoking reading material in the recommended articles series.

This week, we would like to share several latest articles on neurodegenerative diseases from Weidong Le, our Editor-in-Chief.

Title: The essential role of transcription factor Pitx3 in preventing mesodiencephalic dopaminergic neurodegeneration and maintaining neuronal subtype identities during aging
Authors: Ying Wang, Xi Chen, Yuanyuan Wang, Song Li, Huaibin Cai, Weidong Le
Type: Article of Cell Death & Disease
Abstract:
Pituitary homeobox 3 (Pitx3) is required for the terminal differentiation of nigrostriatal dopaminergic neurons during neuronal development. However, whether Pitx3 contributes to the normal physiological function and cell-type identity of adult neurons remains unknown. To explore the role of Pitx3 in maintaining mature neurons, we selectively deleted Pitx3 in the mesodiencephalic dopaminergic (mdDA) neurons of Pitx3^fl/fl/DAT^CreERT2 bigenic mice using a tamoxifen inducible Cre^ERT2/loxp gene-targeting system. Pitx3^fl/fl/DAT^CreERT2 mice developed age-dependent progressive motor deficits, concomitant with a rapid reduction of striatal dopamine (DA) content and a profound loss of mdDA neurons in the substantia nigra pars compacta (SNc) but not in the adjacent ventral tegmental area (VTA), recapitulating the canonical neuropathological features of Parkinson’s disease (PD). Mechanistic studies showed that Pitx3-deficiency significantly increased the number of cleaved caspase-3⁺ cells in SNc, which likely underwent neurodegeneration. Meanwhile, the vulnerability of SNc mdDA neurons was increased in Pitx3^fl/fl/DAT^CreERT2 mice, as indicated by an early decline in glial cell line-derived neurotrophic factor (GDNF) and aldehyde dehydrogenase 1a1 (Aldh1a1) levels. Noticeably, somatic accumulation of α-synuclein (α-syn) was also significantly increased in the Pitx3-deficient neurons. Together, our data demonstrate that the loss of Pitx3 in fully differentiated mdDA neurons results in progressive neurodegeneration, indicating the importance of the Pitx3 gene in adult neuronal survival. Our findings also suggest that distinct Pitx3-dependent pathways exist in SNc and VTA mdDA neurons, correlating with the differential vulnerability of SNc and VTA mdDA neurons in the absence of Pitx3.
Access this article: https://doi.org/10.1038/s41419-021-04319-x

Title: Peripheral Clock System Abnormalities in Patients with Parkinson’s Disease
Authors: Tianbai Li, Cheng Cheng, Congcong Jia, Yue Leng, Jin Qian, Hang Yu, Yufei Liu, Nanxing Wang, Yuting Yang, Murad Al-Nusaif, Weidong Le
Type: Original Research Article of Front. Aging Neurosci.
Abstract:
Objective 
To evaluate the altered expression of peripheral clock genes, circulating melatonin levels, and their correlations with sleep-wake phenotypes including probable rapid eye movement sleep behavior disorder (pRBD) symptoms in a relatively large population of Parkinson’s disease (PD) patients.
Methods 
We determined the expression profiles of five principal clock genes, BMAL₁, CLOCK, CRY₁, PER₁, and PER₂, in the peripheral blood mononuclear cells (PBMCs) of PD patients (n = 326), and healthy controls (HC, n = 314) using quantitative real-time PCR. Melatonin concentration in the plasma of two groups was evaluated by enzyme-linked immunosorbent assay. Then we performed comprehensive association analyses on the PBMCs clock gene expression, plasma melatonin levels and sleep characteristics.
Results
Our data showed that the expression levels of BMAL₁, CLOCK, CRY₁, PER₁, and PER₂ were significantly decreased in the PBMCs of PD as compared with that of HC (P < 0.05). PD patients had reduced plasma melatonin levels compared with HC (P < 0.0001). pRBD and excessive daytime sleepiness are common in these PD patients and are associated with the expression levels of all five clock genes (r = −0.344∼−0.789, P < 0.01) and melatonin concentration (r = −0.509∼−0.753, P < 0.01). Statistical analyses also revealed that a combination of five clock genes and melatonin could reach a high diagnostic performance (areas under the curves, 97%) for PD comorbid pRBD.
Conclusion
This case-control study demonstrates that peripheral BMAL₁, CLOCK, CRY₁, PER₁, PER₂, and melatonin levels are altered in PD patients and may serve as endogenous markers for sleep and wakefulness disturbances of PD.
Access this article: https://doi.org/10.3389/fnagi.2021.736026

Title: Chronic sleep deprivation altered the expression of circadian clock genes and aggravated Alzheimer’s disease neuropathology
Authors: Long Niu, Feng Zhang, Xiaojiao Xu, Yuting Yang, Song Li, Hui Liu, Weidong Le
Type: Research Article of Brain Pathology
Abstract:
Circadian disruption is prevalent in Alzheimer’s disease (AD) and may contribute to cognitive impairment, psychological symptoms, and neurodegeneration. This study aimed to evaluate the effects of environmental and genetic factors on the molecular clock and to establish a link between circadian rhythm disturbance and AD. We investigated the pathological effects of chronic sleep deprivation (CSD) in the APP^swe/PS1^ΔE9 transgenic mice and their wild-type (WT) littermates for 2 months and evaluated the expression levels of clock genes in the circadian rhythm-related nuclei. Our results showed that CSD impaired learning and memory, and further exaggerated disease progression in the AD mice. Furthermore, CSD caused abnormal expression of Bmal1, Clock, and Cry1 in the circadian rhythm-related nuclei of experimental mice, and these changes are more significant in AD mice. Abnormal expression of clock genes in AD mice suggested that the expression of clock genes is affected by APP/PS1 mutations. In addition, abnormal tau phosphorylation was found in the retrosplenial cortex, which was co-located with the alteration of BMAL1 protein level. Moreover, the level of tyrosine hydroxylase in the locus coeruleus of AD and WT mice was significantly increased after CSD. There may be a potential link between the molecular clock, Aβ pathology, tauopathy, and the noradrenergic system. The results of this study provided new insights into the potential link between the disruption of circadian rhythm and the development of AD.
Access this article: https://doi.org/10.1111/bpa.13028