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The Batten disease Palmitoyl Protein Thioesterase 1 gene regulates neural specification and axon connectivity during Drosophila embryonic development.

Chu-LaGraff Q, Blanchette C, O'Hern P, Denefrio C - PLoS ONE (2010)

Bottom Line: Ppt1 embryos display numerous neural defects ranging from abnormal cell fate specification in a number of identified precursor lineages in the CNS, missing and disorganized neurons, faulty motoneuronal axon trajectory, and discontinuous, misaligned, and incorrect midline crossings of the longitudinal axon bundles of the ventral nerve cord.Defects in the PNS include a decreased number of sensory neurons, disorganized chordotonal neural clusters, and abnormally shaped neurons with aberrant dendritic projections.These results indicate that Ppt1 is essential for proper neuronal cell fates and organization; and to establish the local environment for proper axon guidance and fasciculation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Union College, Schenectady, New York, United States of America. chulagrq@union.edu

ABSTRACT
Palmitoyl Protein Thioesterase 1 (PPT1) is an essential lysosomal protein in the mammalian nervous system whereby defects result in a fatal pediatric disease called Infantile Neuronal Ceroids Lipofuscinosis (INCL). Flies bearing mutations in the Drosophila ortholog Ppt1 exhibit phenotypes similar to the human disease: accumulation of autofluorescence deposits and shortened adult lifespan. Since INCL patients die as young children, early developmental neural defects due to the loss of PPT1 are postulated but have yet to be elucidated. Here we show that Drosophila Ppt1 is required during embryonic neural development. Ppt1 embryos display numerous neural defects ranging from abnormal cell fate specification in a number of identified precursor lineages in the CNS, missing and disorganized neurons, faulty motoneuronal axon trajectory, and discontinuous, misaligned, and incorrect midline crossings of the longitudinal axon bundles of the ventral nerve cord. Defects in the PNS include a decreased number of sensory neurons, disorganized chordotonal neural clusters, and abnormally shaped neurons with aberrant dendritic projections. These results indicate that Ppt1 is essential for proper neuronal cell fates and organization; and to establish the local environment for proper axon guidance and fasciculation. Ppt1 function is well conserved from humans to flies; thus the INCL pathologies may be due, in part, to the accumulation of various embryonic neural defects similar to that of Drosophila. These findings may be relevant for understanding the developmental origin of neural deficiencies in INCL.

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Ppt1 LOF mutants exhibit abnormal complement of EVE+ neural precursors and neurons.(A) In wild type, EVE is expressed in GMC4-2.a, the neural precursor that give rise to RP2 motoneuron and its sib (arrow); and in a cluster of GMCs that give rise to the aCC, pCC, CQ neurons (arrowhead). (B–E) In Ppt1 mutants, many hemisegments exhibit a variety of phenotype including the loss of GMC4.2a (arrow in B and E), extra RP2/sib neurons (arrowhead in D), disorganized EVE+ clusters (C), and extra aCC/pCC cells (arrowhead in E). In all panels, embryos are at S11–12 of development; anterior, up; caret, midline.
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pone-0014402-g001: Ppt1 LOF mutants exhibit abnormal complement of EVE+ neural precursors and neurons.(A) In wild type, EVE is expressed in GMC4-2.a, the neural precursor that give rise to RP2 motoneuron and its sib (arrow); and in a cluster of GMCs that give rise to the aCC, pCC, CQ neurons (arrowhead). (B–E) In Ppt1 mutants, many hemisegments exhibit a variety of phenotype including the loss of GMC4.2a (arrow in B and E), extra RP2/sib neurons (arrowhead in D), disorganized EVE+ clusters (C), and extra aCC/pCC cells (arrowhead in E). In all panels, embryos are at S11–12 of development; anterior, up; caret, midline.

Mentions: Results indicate that Ppt1 mutant embryos display abnormal complement of EVE+ GMCs and their progeny in many hemisegments, as early as stage 11/12 of embryogenesis. At stage 11–12, EVE is expressed in GMCs that produce the RP2 motoneuron and its sib; aCC/pCC and U/CQ neurons (Figure 1A). Ppt1 mutant embryos from Df(1)446-20, Ppt1A179T, and Ppt1S77F, and trans-heterozygous Ppt1 mutant crosses show a variety of phenotypes. Some embryos display cellular disorganization where EVE+ GMCs are displaced. In others, there is a loss or gain of extra EVE-positive GMCs and neurons in many hemisegments (Figure 1B–E). The most prevalent phenotype is the loss of GMC4-2.a, the parental precursor that will give rise to the RP2 motoneuron. Occasionally, extra U/CQ and aCC/pCC GMCs are also observed as also the presence of extra RP2s or its sib after GMC4-2.a has divided (Figure 1D–E). Overall, 31% (n = 42) of Ppt1- embryos display abnormality at stage 12. Later in embryonic development during stage 14–15 when the EVE+ GMCs give rise to EVE+ neurons, the loss of EVE+ RP2s is observed in a small, but significant percentage of hemisegments in Ppt1mutants (Figure 2; Table 1). Specifically, over 36% of T1-A8 hemisegments show a loss of RP2s in Df(1)446-20 embryos. Point mutants and trans-heterozygous embryos show 12–17% loss in all hemisegments (Table 1). The degree of penetrance of this EVE neural phenotype is variable: all Df(1)446-20 embryos show at least two missing RP2s whereas Ppt1A179T and Ppt1S77F point mutations range from 32–50%. 63% of embryos from Ppt1A179T×Df(1)446-20 trans-heterozygous crosses and 27% of Ppt1S77F×Df(1)446-20 trans-heterozygous crosses display a partial loss of EVE+ RP2 neurons (Figure 2; Table 2). In contrast, all Ppt1 mutant strains outcrossed to wild type Oregon-R, Df(1)446-20/+, Ppt1A179T/+, and Ppt1S77F/+, all showed normal EVE expression (Tables 1 and 2). These results indicate that the EVE phenotypes are due to the loss of Ppt1.


The Batten disease Palmitoyl Protein Thioesterase 1 gene regulates neural specification and axon connectivity during Drosophila embryonic development.

Chu-LaGraff Q, Blanchette C, O'Hern P, Denefrio C - PLoS ONE (2010)

Ppt1 LOF mutants exhibit abnormal complement of EVE+ neural precursors and neurons.(A) In wild type, EVE is expressed in GMC4-2.a, the neural precursor that give rise to RP2 motoneuron and its sib (arrow); and in a cluster of GMCs that give rise to the aCC, pCC, CQ neurons (arrowhead). (B–E) In Ppt1 mutants, many hemisegments exhibit a variety of phenotype including the loss of GMC4.2a (arrow in B and E), extra RP2/sib neurons (arrowhead in D), disorganized EVE+ clusters (C), and extra aCC/pCC cells (arrowhead in E). In all panels, embryos are at S11–12 of development; anterior, up; caret, midline.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3008717&req=5

pone-0014402-g001: Ppt1 LOF mutants exhibit abnormal complement of EVE+ neural precursors and neurons.(A) In wild type, EVE is expressed in GMC4-2.a, the neural precursor that give rise to RP2 motoneuron and its sib (arrow); and in a cluster of GMCs that give rise to the aCC, pCC, CQ neurons (arrowhead). (B–E) In Ppt1 mutants, many hemisegments exhibit a variety of phenotype including the loss of GMC4.2a (arrow in B and E), extra RP2/sib neurons (arrowhead in D), disorganized EVE+ clusters (C), and extra aCC/pCC cells (arrowhead in E). In all panels, embryos are at S11–12 of development; anterior, up; caret, midline.
Mentions: Results indicate that Ppt1 mutant embryos display abnormal complement of EVE+ GMCs and their progeny in many hemisegments, as early as stage 11/12 of embryogenesis. At stage 11–12, EVE is expressed in GMCs that produce the RP2 motoneuron and its sib; aCC/pCC and U/CQ neurons (Figure 1A). Ppt1 mutant embryos from Df(1)446-20, Ppt1A179T, and Ppt1S77F, and trans-heterozygous Ppt1 mutant crosses show a variety of phenotypes. Some embryos display cellular disorganization where EVE+ GMCs are displaced. In others, there is a loss or gain of extra EVE-positive GMCs and neurons in many hemisegments (Figure 1B–E). The most prevalent phenotype is the loss of GMC4-2.a, the parental precursor that will give rise to the RP2 motoneuron. Occasionally, extra U/CQ and aCC/pCC GMCs are also observed as also the presence of extra RP2s or its sib after GMC4-2.a has divided (Figure 1D–E). Overall, 31% (n = 42) of Ppt1- embryos display abnormality at stage 12. Later in embryonic development during stage 14–15 when the EVE+ GMCs give rise to EVE+ neurons, the loss of EVE+ RP2s is observed in a small, but significant percentage of hemisegments in Ppt1mutants (Figure 2; Table 1). Specifically, over 36% of T1-A8 hemisegments show a loss of RP2s in Df(1)446-20 embryos. Point mutants and trans-heterozygous embryos show 12–17% loss in all hemisegments (Table 1). The degree of penetrance of this EVE neural phenotype is variable: all Df(1)446-20 embryos show at least two missing RP2s whereas Ppt1A179T and Ppt1S77F point mutations range from 32–50%. 63% of embryos from Ppt1A179T×Df(1)446-20 trans-heterozygous crosses and 27% of Ppt1S77F×Df(1)446-20 trans-heterozygous crosses display a partial loss of EVE+ RP2 neurons (Figure 2; Table 2). In contrast, all Ppt1 mutant strains outcrossed to wild type Oregon-R, Df(1)446-20/+, Ppt1A179T/+, and Ppt1S77F/+, all showed normal EVE expression (Tables 1 and 2). These results indicate that the EVE phenotypes are due to the loss of Ppt1.

Bottom Line: Ppt1 embryos display numerous neural defects ranging from abnormal cell fate specification in a number of identified precursor lineages in the CNS, missing and disorganized neurons, faulty motoneuronal axon trajectory, and discontinuous, misaligned, and incorrect midline crossings of the longitudinal axon bundles of the ventral nerve cord.Defects in the PNS include a decreased number of sensory neurons, disorganized chordotonal neural clusters, and abnormally shaped neurons with aberrant dendritic projections.These results indicate that Ppt1 is essential for proper neuronal cell fates and organization; and to establish the local environment for proper axon guidance and fasciculation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Union College, Schenectady, New York, United States of America. chulagrq@union.edu

ABSTRACT
Palmitoyl Protein Thioesterase 1 (PPT1) is an essential lysosomal protein in the mammalian nervous system whereby defects result in a fatal pediatric disease called Infantile Neuronal Ceroids Lipofuscinosis (INCL). Flies bearing mutations in the Drosophila ortholog Ppt1 exhibit phenotypes similar to the human disease: accumulation of autofluorescence deposits and shortened adult lifespan. Since INCL patients die as young children, early developmental neural defects due to the loss of PPT1 are postulated but have yet to be elucidated. Here we show that Drosophila Ppt1 is required during embryonic neural development. Ppt1 embryos display numerous neural defects ranging from abnormal cell fate specification in a number of identified precursor lineages in the CNS, missing and disorganized neurons, faulty motoneuronal axon trajectory, and discontinuous, misaligned, and incorrect midline crossings of the longitudinal axon bundles of the ventral nerve cord. Defects in the PNS include a decreased number of sensory neurons, disorganized chordotonal neural clusters, and abnormally shaped neurons with aberrant dendritic projections. These results indicate that Ppt1 is essential for proper neuronal cell fates and organization; and to establish the local environment for proper axon guidance and fasciculation. Ppt1 function is well conserved from humans to flies; thus the INCL pathologies may be due, in part, to the accumulation of various embryonic neural defects similar to that of Drosophila. These findings may be relevant for understanding the developmental origin of neural deficiencies in INCL.

Show MeSH
Related in: MedlinePlus