library_construction_protocol: In order to obtain a single-cell suspension, mature eVON were cut into 4 parts with a disposable scalpel and incubated with a digestion buffer containing 0.3% collagenase II (Worthington, LS004176) and 0.2% collagenase IV (Worthington, LS0004186) in PBS on a mini rocker shaker at 37ºC (400 rpm) for 30 min. Digestion reaction was blocked with a sequencing buffer containing PBS (without Ca2+ and Mg2+), 2% FBS and 0.5% EDTA 0.5M. The samples were then filtered through 40mm strainers (Falcon, 352340) and centrifuged for 4 min at 1500 rpm at room temperature. Cells were then resuspended in a sequencing buffer, counted and stored at 4ºC until loading on a 10X Genomics microfluidic chip. The single-cell experiment was performed with the 10x Chromium Single Cell 3' v3.1 kit according to manufacturer's instructions. Briefly, cells combined with reverse transcription mix, gel beads, and oil were loaded onto a 10x microfluidic chip to form nanodroplets (GEMs). Each GEM contained a cell where first-strand cDNA synthesis occurred, tagging each mRNA with a unique molecular identifier  (UMI) and a cell-specific barcode. Droplets were broken, fractions were pooled and purified using Dynabeads MyOne Silane, and cDNA was amplified with PCR. Single-cell libraries were prepared through fragmentation, end repair, A-tailing, and double-sided size selection with SPRIselect Reagent. P5 and P7 adapters were ligated, and individual sample indices from Dual Index Plate were added for pooling and later demultiplexing of libraries. Library quality and quantity were checked with high-sensitivity DNA assays on an Agilent Bioanalyzer and Fragment Analyzer.