The LIPIN1 gene encodes Lipin-1, a Mg(++)-dependent phosphatidic acid phosphatase. The latter protein is 890 amino acid long, with two conserved domains; an N-terminal domain encompassing the first 114 residues, and a catalytic domain LNS2 (Lipin/Ned1/Smp2) at amino acids 674-830. Lipin-1 catalyzes the conversion of phosphatidic acid to diacylglycerol in the triacylglycerol synthesis pathway.
LPIN1 expression is most prominent in skeletal muscle and adipose tissue in humans. Lipin mRNA levels in human adipose tissue have a strong negative correlation with fasting glucose and insulin levels, and they can serve as an indicator of insulin resistance.
The LIPIN1 gene resides on chromosome 2 with 21 exons. A number of LPIN1 mutations were identified in patients with autosomal recessive recurrent myoglobinuria. These mutations were found to introduce a stop codon at residues 215, 388, and 800, or cause frame shifts as a result of skipping exons, consequently, they are expected to result in truncated proteins lacking catalytic activity. These defects were postulated to cause the accumulation of lysophosphatidate and other lysophospholipids in muscle tissue, which can lead to rhabdomyolysis. On the other hand, a heterozygous mutation in the LPIN1 gene (p.E769G) may predispose for statin-induced myopathy.
Zeharia et al. (2008) described three patients of Arab origin who developed recurrent myoglobinuria beginning at 2, 2, and 7 years of age, respectively. Zeharia et al. (2008) used homozygosity mapping to link the disorder to certain nonsense and frameshift mutations in the LPIN1 gene.