“…The global transcriptomic landscape of the vertebrate OM is similar between individuals and broadly conserved among different vertebrate species, ranging from zebrafish to human ( Bear et al, 2016 ; Saraiva et al, 2015a , 2019 ). Similarly, the spatial segregation of Olfrs into partially overlapping rings of expression, centered around the midline structure of the OM, is also conserved among vertebrates ( Freitag et al, 1995 ; Horowitz et al, 2014 ; Marchand et al, 2004 ; Miyamichi et al, 2005 ; Octura et al, 2018 ; Ressler et al, 1993 ; Strotmann et al, 1992 ; Vassar et al, 1993 ; Weth et al, 1996 ). While the number of Olfr zones in zebrafish, frog, and salamander still remain unknown ( Freitag et al, 1995 ; Marchand et al, 2004 ; Weth et al, 1996 ), ISH studies suggested that the total number of Olfr expression zones can vary between mammals—ranging from two in macaque ( Horowitz et al, 2014 ) to four in rat ( Vassar et al, 1993 ) and goat ( Octura et al, 2018 ), and between four and nine in mouse ( Miyamichi et al, 2005 ; Ressler et al, 1993 ; Zapiec and Mombaerts, 2020 ).…”