Increased Ubqln2 expression causes neuron death in transgenic rats.

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Pathogenic mutations in ubiquilin 2 (UBQLN2) are linked to neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD).
• Previous research in animal models indicated that these diseases arise from a toxic gain of function, rather than a loss of function, associated with UBQLN2 mutations.
• The precise mechanism by which UBQLN2 mutations induce neurodegeneration remains unclear.

Purpose of the Study:

• To investigate whether an enhanced function of wild-type UBQLN2 contributes to the pathogenesis observed in UBQLN2-related neurodegenerative diseases.
• To develop a more relevant animal model for studying UBQLN2-associated neurodegeneration.

Main Methods:

• Created transgenic rats over-expressing wild-type human UBQLN2.
• Generated transgenic rats over-expressing wild-type rat Ubqln2 to account for potential species-specific interactions.
• Assessed neuronal function, spatial learning, and the formation of protein inclusions in the created transgenic rat models.

Main Results:

• Over-expression of both human and rat wild-type Ubqln2 in transgenic rats led to neuronal death and spatial learning deficits.
• The observed pathologies were similar to those seen in transgenic rats with pathogenic UBQLN2 mutations.
• Excess wild-type UBQLN2 formed protein aggregates that attracted key cellular components involved in protein degradation pathways (sequestosome-1 and 26S proteasome).

Conclusions:

• The findings suggest that an overabundance of UBQLN2, irrespective of mutation, is detrimental to neuronal health.
• Enhanced or uncontrolled UBQLN2 function, not solely its mutation, plays a significant role in the pathogenesis of UBQLN2-related neurodegenerative diseases.
• These results highlight the potential toxicity of elevated UBQLN2 levels and implicate functional enhancement in disease mechanisms.