Table 1. Highlighted examples of molecular and cellular processes prior to luminal connection across different organisms.

Cellular Process	Developmental System	Associated molecules	Organism	References
Basement membrane dissolution	Primary mouth formation	Wnt antagonists	Xenopus laevis	Dickinson and Sive1,4
	Uterus-vulva connection	Netrin Fos-1 HLH-2 INA-1/PAT-3 VAB-19	C. elegans	Ziel et al. 11 Sherwood et al.10 Schindler et al.14 Ihara et al.2
Apoptosis	Primary mouth	Unknown	Xenopus laevis	Dickinson and Sive 4
	Cloacal formation	Bmp	Danio rerio	Pyati et al.5
	Ureter repositioning	Ret, Raldh	Mus musculus	Batourina et al.3
Cell rearrangement and/or movement of adhesive junctions	Thinning and perforation	Unknown	Xenopus laevis	Dickinson and Sive4
	Cloacal formation	Bmp Wtip (Ajuba)	Danio rerio	Pyati et al.5 Bubenshchikova et al. 25
	Branchial fusion	Unknown	Botryllus schlosseri	Manni et al.24
	Vessel fusion	Moesin1,Ve-cadherin ZO-1	Danio rerio	Wang et al. 38 Herwig et al.36 Blum et al.37
Invasive behavior	Anchor cell invasion	Netrin Integrin	C. elegans	Ziel et al.11 Hagedorn et al.12
	Cytoplasmic extensions (Primary ureter- bladder fusion)	Gata3 Raldh	Mus musculus	Chia et al.45
	Distal cell invasion (mouse kidney)	Unknown	Mus musculus	Kao et al.18