Table 1.

Frequencies of V_H replacement footprint motifs in the N1 and N2 regions of human IgH genes.

	Total number of sequences	Sequences with VH, DH, JH gene assignmenta	Length of VH replacement footprint	VH replacement footprint motifs in N1	VH replacement footprint motifs in N2	p-Valueb	Frequency of VH replacement products (%)c
Test IgH sequencesd	417	396	3	217	140	0.0001	54.7
			4	99	64	0.0028	25.0
			5	29	15	0.0437	7.3
			6	5	3e	NAf	NAf
			7	2	0	NAf	NAf
NCBI IgH sequencesg	61,851	39,438	3	23,195	20,699	0.0001	58.8
			4	13,365	11,240	0.0001	33.9
			5	4788	3499	0.0001	12.1
			6	1490	813	0.0001	4.3
			7	382	140	0.0001	1.1

^aUnique IgH gene sequences with identifiable V_H, D_H, and J_H genes were analyzed. These IgH sequences contain both functional and non-functional IgH rearrangements. N1, V_H–D_H junction regions; N2, D_H–J_H junction regions.

^bThe frequencies of V_H replacement footprint motifs with different length within the N1 or the N2 regions were compared by two-tailed Chi square with Yates’ correction. p < 0.05 is considered statistically significant and p < 0.0001 is considered extremely statistically significant.

^cThe frequency of V_H replacement products was calculated using the number of sequences with V_H replacement motifs with different length in the N1 regions divided by the total number of unique IgH gene sequences.

^dThese IgH gene sequences had been analyzed manually for V_H replacement products (37).

^eAll the three 6-mer footprints within the N2 regions could be due to second D_H gene segments.

^fNot applicable.

^gThe human IgH gene sequence dataset was downloaded from the NCBI database on April 20, 2011.