What is claimed is:1. A display apparatus comprising:a first semiconductor layer disposed on a substrate;a first gate layer disposed on the first semiconductor layer, the first gate layer including a driving gate electrode;a second gate layer disposed on the first gate layer, the second gate layer including a capacitor upper electrode;a first connecting electrode layer disposed on the second gate layer, the first connecting electrode layer including a transfer wiring;a second connecting electrode layer disposed on the first connecting electrode layer, the second connecting electrode layer including a horizontal connection wiring extending in a first direction;a third connecting electrode layer disposed on the second connecting electrode layer, the third connecting electrode layer including a vertical connection wiring extending in a second direction that intersects the first direction;a light-emitting diode including a pixel electrode disposed on the vertical connection wiring; andan insulating layer disposed between the vertical connection wiring and the pixel electrode of the light-emitting diode.2. The display apparatus of claim 1, whereinthe third connecting electrode layer includes a data wiring extending in the second direction, andthe vertical connection wiring is electrically connected to the data wiring and the horizontal connection wiring.3. The display apparatus of claim 2, whereinthe substrate includes:a display area; anda peripheral area adjacent to the display area, andthe vertical connection wiring is electrically connected to the data wiring in the peripheral area.4. The display apparatus of claim 3, wherein the vertical connection wiring and the data wiring are integral with each other.5. The display apparatus of claim 3, wherein the horizontal connection wiring is electrically connected to the vertical connection wiring in the display area.6. The display apparatus of claim 3, whereinthe vertical connection wiring is electrically connected to the horizontal connection wiring via a contact hole, andthe second connecting electrode layer includes an auxiliary horizontal connection wiring that is spaced apart from the horizontal connection wiring to be electrically disconnected from the horizontal connection wiring and the data wiring and that extends parallel to the horizontal connection wiring.7. The display apparatus of claim 3, whereinthe vertical connection wiring is electrically connected to the horizontal connection wiring via a contact hole, andthe third connecting electrode layer includes an auxiliary vertical connection wiring that is spaced apart from the vertical connection wiring to be electrically disconnected from the horizontal connection wiring and the vertical connection wiring and that extends parallel to the vertical connection wiring.8. The display apparatus of claim 3, wherein the third connecting electrode layer includes an additional vertical connection wiring that extends in the second direction and is electrically connected to the horizontal connection wiring in the display area.9. The display apparatus of claim 8, wherein the third connecting electrode layer includes an auxiliary additional vertical connection wiring that is spaced apart from the additional vertical connection wiring to be electrically disconnected from the horizontal connection wiring and the additional vertical connection wiring and that extends parallel to the additional vertical connection wiring.10. The display apparatus of claim 1, whereinthe third connecting electrode layer includes a data wiring extending in the second direction,the substrate includes:a display area; anda peripheral area adjacent to the display area, andthe horizontal connection wiring is electrically connected to the data wiring in the display area.11. The display apparatus of claim 10, wherein the data wiring is electrically connected to the horizontal connection wiring via a contact hole.12. The display apparatus of claim 11, wherein the second connecting electrode layer includes an auxiliary horizontal connection wiring that is spaced apart from the horizontal connection wiring to be electrically disconnected from the horizontal connection wiring and the data wiring and that extends parallel to the horizontal connection wiring.13. The display apparatus of claim 10, wherein the vertical connection wiring is electrically connected to the data wiring and the horizontal connection wiring.14. The display apparatus of claim 13, wherein the vertical connection wiring intersects the horizontal connection wiring.15. The display apparatus of claim 10, wherein the third connecting electrode layer includes an additional vertical connection wiring that extends in the second direction and is electrically connected to the horizontal connection wiring in the display area.16. The display apparatus of claim 15, wherein the third connecting electrode layer includes an auxiliary additional vertical connection wiring that is spaced apart from the additional vertical connection wiring to be electrically disconnected from the horizontal connection wiring and the additional vertical connection wiring and that extends parallel to the additional vertical connection wiring.17. A display apparatus comprising:a first semiconductor layer disposed on a substrate;a first gate layer disposed on the first semiconductor layer, the first gate layer including a driving gate electrode;a second gate layer disposed on the first gate layer, the second gate layer including a capacitor upper electrode;a first connecting electrode layer disposed on the second gate layer, the first connecting electrode layer including a transfer wiring;a second connecting electrode layer disposed on the first connecting electrode layer, the second connecting electrode layer including a horizontal connection wiring extending in a first direction;a third connecting electrode layer disposed on the second connecting electrode layer, the third connecting electrode layer including a vertical connection wiring extending in a second direction that intersects the first direction;a second semiconductor layer between the second gate layer and the first connecting electrode layer; anda third gate layer between the second semiconductor layer and the first connecting electrode layer, the third gate layer including a compensation gate electrode.18. The display apparatus of claim 17, wherein the third gate layer includes a gate wiring extending in the first direction.19. The display apparatus of claim 18, wherein, the gate wiring intersects the vertical connection wiring.20. The display apparatus of claim 17, whereinthe first semiconductor layer includes polysilicon, andthe second semiconductor layer includes an oxide semiconductor.21. A display apparatus comprising:an organic light-emitting diode;a driving transistor that controls an amount of current flowing from a first node to the organic light-emitting diode in response to a voltage applied to a second node, the first node being electrically connected to a driving voltage line;a switching transistor that transfers a data signal from a data line to the first node, in response to a voltage applied to a scan line;an initialization transistor that applies an initialization voltage from an initialization voltage line to the second node, in response to a voltage applied to a previous scan line, the initialization transistor including an initialization semiconductor layer disposed on an insulating layer that overlaps a driving semiconductor layer included in the driving transistor;a transfer wiring disposed on an insulating layer that overlaps an initialization gate electrode included in the initialization transistor, the transfer wiring electrically connecting the initialization semiconductor layer to a driving gate electrode included in the driving transistor;a horizontal connection wiring disposed on an insulating layer that overlaps the transfer wiring and extending in a first direction; anda vertical connection wiring disposed on an insulating layer that overlaps the horizontal connection wiring and extending in a second direction intersecting the first direction.22. The display apparatus of claim 21, wherein the vertical connection wiring is electrically connected to the horizontal connection wiring via a contact hole formed in the insulating layer that overlaps the horizontal connection wiring.23. The display apparatus of claim 21, whereinthe driving semiconductor layer includes polysilicon, andthe initialization semiconductor layer includes an oxide semiconductor.24. The display apparatus of claim 21, wherein the data line and the vertical connection wiring are disposed on a same layer.25. The display apparatus of claim 24, wherein the data line extends in the second direction.26. The display apparatus of claim 21, wherein the driving voltage line and the vertical connection wiring are disposed on a same layer.