Arabidopsis (Arabidopsis thaliana) has eight glycerol-3-phosphate acyltransferase (GPAT) genes that are members of a plantspecific family with three distinct clades. Several of these GPATs are required for the synthesis of cutin or suberin. Unlike GPATs with sn-1 regiospecificity involved in membrane or storage lipid synthesis, GPAT4 and -6 are unique bifunctional enzymes with both sn-2 acyltransferase and phosphatase activity resulting in 2-monoacylglycerol products. We present enzymology, pathway organization, and evolutionary analysis of this GPAT family. Within the cutin-associated clade, GPAT8 is demonstrated as a bifunctional sn-2 acyltransferase/phosphatase. GPAT4, -6, and -8 strongly prefer C16:0 and C18:1 v-oxidized acyl-coenzyme As (CoAs) over unmodified or longer acyl chain substrates. In contrast, suberin-associated GPAT5 can accommodate a broad chain length range of v-oxidized and unsubstituted acyl-CoAs. These substrate specificities (1) strongly support polyester biosynthetic pathways in which acyl transfer to glycerol occurs after oxidation of the acyl group, (2) implicate GPAT specificities as one major determinant of cutin and suberin composition, and (3) argue against a role of sn-2-GPATs (Enzyme Commission 2.3.1.198) in membrane/storage lipid synthesis. Evidence is presented that GPAT7 is induced by wounding, produces suberin-like monomers when overexpressed, and likely functions in suberin biosynthesis. Within the third clade, we demonstrate that GPAT1 possesses sn-2 acyltransferase but not phosphatase activity and can utilize dicarboxylic acyl-CoA substrates. Thus, sn-2 acyltransferase activity extends to all subbranches of the Arabidopsis GPAT family. Phylogenetic analyses of this family indicate that GPAT4/6/8 arose early in land-plant evolution (bryophytes), whereas the phosphatase-minus GPAT1 to -3 and GPAT5/7 clades diverged later with the appearance of tracheophytes.

The first step in assembly of membrane and storage glycerolipids is acylation of glycerol-3-phosphate (G3P). All previously characterized membrane-bound, eukaryotic G3P acyltransferases (GPATs) acylate the sn-1 position to produce lysophosphatidic acid (1-acyl-LPA). Cutin is a glycerolipid with omega-oxidized fatty acids and glycerol as integral components. It occurs as an extracellular polyester on the aerial surface of all plants, provides a barrier to pathogens and resistance to stress, and maintains organ identity. We have determined that Arabidopsis acyltransferases GPAT4 and GPAT6 required for cutin biosynthesis esterify acyl groups predominantly to the sn-2 position of G3P. In addition, these acyltransferases possess a phosphatase domain that results in sn-2 monoacylglycerol (2-MAG) rather than LPA as the major product. Such bifunctional activity has not been previously described in any organism. The possible roles of 2-MAGs as intermediates in cutin synthesis are discussed. GPAT5, which is essential for the accumulation of suberin aliphatics, also exhibits a strong preference for sn-2 acylation. However, phosphatase activity is absent and 2-acyl-LPA is the major product. Clearly, plant GPATs can catalyze more reactions than the sn-1 acylation by which they are currently categorized. Close homologs of GPAT4-6 are present in all land plants, but not in animals, fungi or microorganisms (including algae). Thus, these distinctive acyltransferases may have been important for evolution of extracellular glycerolipid polymers and adaptation of plants to a terrestrial environment. These results provide insight into the biosynthetic assembly of cutin and suberin, the two most abundant glycerolipid polymers in nature.cutin | suberin | lysophosphatidic acid phosphatase | bifunctional G lycerol-3-phosphate acyltransferase (GPAT) (EC 2.3.1.15) catalyzes the initial step of glycerolipid synthesis, the incorporation of an acyl group from acyl-CoA onto the sn-1 position of sn-glycerol-3-phosphate (G3P) to yield 1-acyl-lysophosphatidic acid (1-acyl-LPA). This reaction has been extensively characterized in bacteria, fungi, animals, and plants (1-5). A family of eight plant GPAT acyltransferase genes in Arabidopsis was first identified based on sequence similarity to known nonplant GPAT enzymes. When expressed in yeast, several members of the family were shown to catalyze acyl transfer to G3P, although the position on glycerol that was acylated was not determined (6).Cutin and suberin are lipophilic barriers found associated with the plant cell wall. They have broadly similar functions in that they control small molecule fluxes and act as protective barriers. The major components of both cutin and the aliphatic domain of suberin are ω-oxidized fatty acids, namely ω-hydroxy fatty acids (ω-OHFAs) and α,ω-dicarboxylic acids (DCAs), with varying amounts of glycerol. Thus, cutin and suberin are also glycerolipids (7,8). Although it is one of the most abundant lipid polymers in nature, with an area five times earth's land surface ...

Huntington's disease (HD) is characterized by preferential loss of the medium spiny neurons in the striatum. Using CRISPR/Cas9 and somatic nuclear transfer technology, we established a knockin (KI) pig model of HD that endogenously expresses full-length mutant huntingtin (HTT). By breeding this HD pig model, we have successfully obtained F1 and F2 generation KI pigs. Characterization of founder and F1 KI pigs shows consistent movement, behavioral abnormalities, and early death, which are germline transmittable. More importantly, brains of HD KI pig display striking and selective degeneration of striatal medium spiny neurons. Thus, using a large animal model of HD, we demonstrate for the first time that overt and selective neurodegeneration seen in HD patients can be recapitulated by endogenously expressed mutant proteins in large mammals, a finding that also underscores the importance of using large mammals to investigate the pathogenesis of neurodegenerative diseases and their therapeutics.

CRISPR/Cas9 has been used to genetically modify genomes in a variety of species, including non-human primates. Unfortunately, this new technology does cause mosaic mutations, and we do not yet know whether such mutations can functionally disrupt the targeted gene or cause the pathology seen in human disease. Addressing these issues is necessary if we are to generate large animal models of human diseases using CRISPR/Cas9. Here we used CRISPR/Cas9 to target the monkey dystrophin gene to create mutations that lead to Duchenne muscular dystrophy (DMD), a recessive X-linked form of muscular dystrophy. Examination of the relative targeting rate revealed that Crispr/Cas9 targeting could lead to mosaic mutations in up to 87% of the dystrophin alleles in monkey muscle. Moreover, CRISPR/Cas9 induced mutations in both male and female monkeys, with the markedly depleted dystrophin and muscle degeneration seen in early DMD. Our findings indicate that CRISPR/Cas9 can efficiently generate monkey models of human diseases, regardless of inheritance patterns. The presence of degenerated muscle cells in newborn Cas9-targeted monkeys suggests that therapeutic interventions at the early disease stage may be effective at alleviating the myopathy.