A Single Complex Agpat2 Allele in a Patient With Partial Lipodystrophy

Area of Science:

• Genetics
• Endocrinology
• Rare Diseases

Background:

• Genetic lipodystrophies are rare syndromes causing severe metabolic complications like insulin resistance and hypertriglyceridemia.
• These syndromes are classified by adipose tissue distribution (local, partial, general) but diagnosis is challenging due to genetic heterogeneity.
• Over 18 genes are implicated, with mutations in AGPAT2 previously linked only to generalized lipodystrophy.

Purpose of the Study:

• To investigate the genetic cause of partial lipodystrophy in an adult female patient with metabolic complications.
• To analyze the function of a novel complex AGPAT2 allele identified in the patient.
• To explore the implications of the findings for the classification and understanding of lipodystrophies.

Main Methods:

• Whole genome sequencing (WGS) was used to identify genetic variants.
• In vitro enzymatic activity assays using mass spectrometry were performed on the identified AGPAT2 double mutant.
• SNP risk score analysis was conducted to assess genetic predisposition.

Main Results:

• A single complex AGPAT2 allele [V67M;V167A] was identified, functionally equivalent to heterozygosity, in a patient with partial lipodystrophy.
• The identified AGPAT2 double mutant was found to be enzymatically inactive.
• SNP risk score analysis indicated no genetic predisposition to lipodystrophy in the patient, suggesting the AGPAT2 variants were causative.

Conclusions:

• The findings suggest that the current classification of lipodystrophies may need re-evaluation towards a continuum of clinical presentation and genetic causes.
• A novel complex AGPAT2 allele can cause partial lipodystrophy, expanding the known genotype-phenotype correlations for this gene.
• Further molecular understanding of lipodystrophies could pave the way for novel therapeutic strategies for adipose tissue dysfunction.